Sfc to fc (#124)

📖Update to use FC and not SFC
DefinitelyTyped/DefinitelyTyped#30364

By  @Pau1fitz:
* Initial work

By @piotrwitek 
* rebase on master
* Refactored all references related to SFC, stateless & stateful in favour of function and class components
* Other minor improvements

Author: piotrwitek

CONTRIBUTING.md

@@ -22,8 +22,8 @@ Don't edit `README.md` directly - it is generated automatically from `README_SOU
 **Source code inject directives:**
 ```
 # Inject code block with highlighter
-::codeblock='playground/src/components/sfc-counter.tsx'::
+::codeblock='playground/src/components/fc-counter.tsx'::
 
 # Inject code block with highlighter and expander
-::expander='playground/src/components/sfc-counter.usage.tsx'::
+::expander='playground/src/components/fc-counter.usage.tsx'::
 ```