Specify from which version

docs/guide/browser-compatibility.md

@@ -89,6 +89,12 @@ Vue CLI uses two environment variables to communicate this:
 **Important:** These variables are only accessible when/after `chainWebpack()` and `configureWebpack()` functions are evaluated, (so not directly in the `vue.config.js` module's root scope). That means it's also available in the postcss config file.
 :::
 
+::: warning Caveat: Adjusting webpack plugins
+Some Plugins, i.e. `html-webpack-plugin`, `preload-plugin` etc. are only included in the config for modern mode. Trying to tap into their options in the legacy config can throw an error as the plugins don't exist.
+
+Use the above tip about *Detecting the Current Mode* to manipulate plugins in the right mode only, and/or check if the plugin actually exists in the current mode's config before trying to tap into their options.
+:::
+
 [autoprefixer]: https://github.com/postcss/autoprefixer
 [babel-preset-env]: https://new.babeljs.io/docs/en/next/babel-preset-env.html
 [babel-preset-app]: https://github.com/vuejs/vue-cli/tree/dev/packages/%40vue/babel-preset-app

docs/guide/deployment.md

@@ -261,7 +261,35 @@ npm install -g now
 
 ### Heroku
 
-> TODO | Open to contribution.
+1. [Install Heroku CLI](https://devcenter.heroku.com/articles/heroku-cli)
+
+2. Create a `static.json` file:
+```json
+{
+  "root": "dist",
+  "clean_urls": true,
+  "routes": {
+    "/**": "index.html"
+  }
+}
+```
+
+3. Add `static.json` file to git
+```bash
+git add static.json
+git commit -m "add static configuration"
+```
+
+4. Deploy to Heroku
+```bash
+heroku login
+heroku create
+heroku buildpacks:add heroku/nodejs
+heroku buildpacks:add https://github.com/heroku/heroku-buildpack-static
+git push heroku master
+```
+
+More info: https://gist.github.com/hone/24b06869b4c1eca701f9
 
 ### Surge