Make README markdown more consistent (#8705)

* Make README markdown more consistent
* Most lines were 80 characters wide, others not - make them all 80.
* Switch to === titles in README where possible

Author: andybalaam

README.md

@@ -22,17 +22,18 @@ a 'skin'. A skin provides:
  * The containing application
  * Zero or more 'modules' containing non-UI functionality
 
-As of Aug 2018, the only skin that exists is [`vector-im/element-web`](https://github.com/vector-im/element-web/); it and
+As of Aug 2018, the only skin that exists is
+[`vector-im/element-web`](https://github.com/vector-im/element-web/); it and
 `matrix-org/matrix-react-sdk` should effectively
 be considered as a single project (for instance, matrix-react-sdk bugs
 are currently filed against vector-im/element-web rather than this project).
 
 Translation Status
-==================
+------------------
 [![Translation status](https://translate.element.io/widgets/element-web/-/multi-auto.svg)](https://translate.element.io/engage/element-web/?utm_source=widget)
 
 Developer Guide
-===============
+---------------
 
 Platform Targets:
  * Chrome, Firefox and Safari.
@@ -51,21 +52,25 @@ Please follow the Matrix JS/React code style as per:
 https://github.com/matrix-org/matrix-react-sdk/blob/master/code_style.md
 
 Code should be committed as follows:
- * All new components: https://github.com/matrix-org/matrix-react-sdk/tree/master/src/components
- * Element-specific components: https://github.com/vector-im/element-web/tree/master/src/components
-   * In practice, `matrix-react-sdk` is still evolving so fast that the maintenance
-     burden of customising and overriding these components for Element can seriously
-     impede development.  So right now, there should be very few (if any) customisations for Element.
+ * All new components:
+   https://github.com/matrix-org/matrix-react-sdk/tree/master/src/components
+ * Element-specific components:
+   https://github.com/vector-im/element-web/tree/master/src/components
+   * In practice, `matrix-react-sdk` is still evolving so fast that the
+     maintenance burden of customising and overriding these components for
+     Element can seriously impede development.  So right now, there should be
+     very few (if any) customisations for Element.
  * CSS: https://github.com/matrix-org/matrix-react-sdk/tree/master/res/css
- * Theme specific CSS & resources: https://github.com/matrix-org/matrix-react-sdk/tree/master/res/themes
+ * Theme specific CSS & resources:
+   https://github.com/matrix-org/matrix-react-sdk/tree/master/res/themes
 
 React components in matrix-react-sdk come in two different flavours:
 'structures' and 'views'.  Structures are stateful components which handle the
 more complicated business logic of the app, delegating their actual presentation
 rendering to stateless 'view' components.  For instance, the RoomView component
-that orchestrates the act of visualising the contents of a given Matrix chat room
-tracks lots of state for its child components which it passes into them for visual
-rendering via props.
+that orchestrates the act of visualising the contents of a given Matrix chat
+room tracks lots of state for its child components which it passes into them for
+visual rendering via props.
 
 Good separation between the components is maintained by adopting various best
 practices that anyone working with the SDK needs to be aware of and uphold:
@@ -82,18 +87,19 @@ practices that anyone working with the SDK needs to be aware of and uphold:
 
   * Per-view CSS is optional - it could choose to inherit all its styling from
     the context of the rest of the app, although this is unusual for any but
- * Theme specific CSS & resources: https://github.com/matrix-org/matrix-react-sdk/tree/master/res/themes
-    structural components (lacking presentation logic) and the simplest view
-    components.
+ * Theme specific CSS & resources:
+   https://github.com/matrix-org/matrix-react-sdk/tree/master/res/themes
+   structural components (lacking presentation logic) and the simplest view
+   components.
 
   * The view MUST *only* refer to the CSS rules defined in its own CSS file.
     'Stealing' styling information from other components (including parents)
     is not cool, as it breaks the independence of the components.
 
-  * CSS classes are named with an app-specific name-spacing prefix to try to avoid
-    CSS collisions.  The base skin shipped by Matrix.org with the matrix-react-sdk
-    uses the naming prefix "mx_".  A company called Yoyodyne Inc might use a
-    prefix like "yy_" for its app-specific classes.
+  * CSS classes are named with an app-specific name-spacing prefix to try to
+    avoid CSS collisions.  The base skin shipped by Matrix.org with the
+    matrix-react-sdk uses the naming prefix "mx_".  A company called Yoyodyne
+    Inc might use a prefix like "yy_" for its app-specific classes.
 
   * CSS classes use upper camel case when they describe React components - e.g.
     .mx_MessageTile is the selector for the CSS applied to a MessageTile view.
@@ -130,13 +136,13 @@ the distinction between 'structural' and 'view' components, so we backed away
 from it.
 
 Github Issues
-=============
+-------------
 
 All issues should be filed under https://github.com/vector-im/element-web/issues
 for now.
 
 Development
-===========
+-----------
 
 Ensure you have the latest LTS version of Node.js installed.
 
@@ -145,9 +151,10 @@ guide](https://classic.yarnpkg.com/docs/install) if you do not have it
 already. This project has not yet been migrated to Yarn 2, so please ensure
 `yarn --version` shows a version from the 1.x series.
 
-`matrix-react-sdk` depends on [`matrix-js-sdk`](https://github.com/matrix-org/matrix-js-sdk). To make use of changes in the
-latter and to ensure tests run against the develop branch of `matrix-js-sdk`,
-you should set up `matrix-js-sdk`:
+`matrix-react-sdk` depends on
+[`matrix-js-sdk`](https://github.com/matrix-org/matrix-js-sdk). To make use of
+changes in the latter and to ensure tests run against the develop branch of
+`matrix-js-sdk`, you should set up `matrix-js-sdk`:
 
 ```bash
 git clone https://github.com/matrix-org/matrix-js-sdk
@@ -170,16 +177,17 @@ yarn install
 See the [help for `yarn link`](https://classic.yarnpkg.com/docs/cli/link) for
 more details about this.
 
-Running tests
-=============
+### Running tests
 
 Ensure you've followed the above development instructions and then:
 
 ```bash
 yarn test
 ```
 
-## End-to-End tests
+### End-to-End tests
 
-Make sure you've got your Element development server running (by doing `yarn start` in element-web), and then in this project, run `yarn run e2etests`.
-See [`test/end-to-end-tests/README.md`](https://github.com/matrix-org/matrix-react-sdk/blob/develop/test/end-to-end-tests/README.md) for more information.
+Make sure you've got your Element development server running (by doing `yarn
+start` in element-web), and then in this project, run `yarn run e2etests`. See
+[`test/end-to-end-tests/README.md`](https://github.com/matrix-org/matrix-react-sdk/blob/develop/test/end-to-end-tests/README.md)
+for more information.