Issue 3692 - Add base ESLint configuration

eslint-config-eyeo/README.md

 # eslint-config-eyeo
 
 An [ESLint](http://eslint.org) configuration that checks for compliance with the
 [Adblock Plus coding style guide](https://adblockplus.org/coding-style#javascript)
 which is used for all eyeo projects.
 
 ## Installation
 
     npm install -g eslint eslint-config-eyeo
 
-(As root, or using sudo.)
+This command requires administrator privileges so you might need to use `sudo`.
 
 ## Usage
 
-To lint a JavaScript file using ESLint you simply run the `eslint` command with
-the file as an argument. For example:
+To lint a JavaScript file using ESLint you run the `eslint` command with the
+file as an argument. For example:
 
     eslint some-file.js
 
-(For advanced usage see `eslint --help`.)
+For advanced usage see `eslint --help`.
 
-All of our projects which use much JavaScript should eventually have
-their own ESLint configuration which inherits from this base
-configuration. A minimal example:
+In order to use eslint-config-eyeo your project's ESLint configuration
+should extend from it. A minimal example looks like this:
 
     {
       "extends": "eslint-config-eyeo",
       "root": true
     }
 
-In the mean time if you need to lint files inside projects which do

[Sebastian Noack, 2017/02/12 20:53:11]

I don't like the duplication here. How about:

  In order to use eslint-config-eyeo,
  add following option to your .eslintrc.json
  (or put it in your ~/.eslintrc.json in order
  to lint projects that don't have an own
  configuration file):

(Or something along these lines) followed by the snippet.

[kzar, 2017/02/13 06:02:58]

OK, I've had another go. What do you think?

-not yet have an ESLint configuration you can create a personal
-configuration in `~/.eslintrc.json` like so:
-
-    {
-      "extends": "eslint-config-eyeo"
-    }
+For projects without an ESLint configuration you can create your own
+personal configuration in `~/.eslintrc.json`, but take care to remove
+the `"root": true` section from the above example.