Issue 5109 - Create stylelintrc for websites and ui modules

stylelint-config-eyeo/README.md

Index: stylelint-config-eyeo/README.md
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+# stylelint-config-eyeo
+
+A [Stylelint](https://stylelint.io) configuration that checks for compliance
+with the [Adblock Plus coding style guide](https://adblockplus.org/coding-style#html-css)
+which is used for all eyeo projects.
+
+## Installation
+
+    npm install -g stylelint
+
+This command requires administrator privileges so you might need to use `sudo`.
+
+Next, either install stylelint-config-eyeo within your project. For example:
+
+    npm install --save-dev stylelint-config-eyeo
+
+Or, install stylelint-config-eyeo globally. For example:
+
+    npm install -g stylelint-config-eyeo
+
+## Usage
+
+To lint a CSS (or CSS-like, e.g. SCSS, SugarCSS, Less) file using Stylelint
+you run the `stylelint` command with the file as an argument. For example:
+
+    stylelint example.css
+
+For advanced usage see `stylelint --help`.
+
+In order to use stylelint-config-eyeo, your project's Stylelint configuration
+should extend from it. A minimal example looks like this:
+
+    {
+      "extends": "stylelint-config-eyeo"
+    }
+
+If you've globally installed stylelint-config-eyeo using the `-g` flag, then
+you'll need to use the absolute path to stylelint-config-eyeo in your config.
+
+    {
+      "extends": "/absolute/path/to/stylelint-config-eyeo"
+    }
+
+For projects without a Stylelint configuration you can create your own
+personal configuration in `~/.stylelintrc.json`.