DEV: uses central eslint-config-discourse (#8150)

* DEV: uses centrain eslint-config-discourse

Discourse project or plugins can now have a central configuration by doing:

`yarn add  --dev eslint-config-discourse@latest`

* adds postinstall script

.eslintrc

@@ -1,96 +1,3 @@
 {
-  "env": {
-    "browser": true,
-    "builtin": true,
-    "es6": true,
-    "jasmine": true,
-    "mocha": true,
-    "node": true
-  },
-  "parserOptions": {
-    "ecmaVersion": 7,
-    "sourceType": "module"
-  },
-  "globals": {
-    "$": true,
-    "_": true,
-    "andThen": true,
-    "asyncRender": true,
-    "Blob": true,
-    "bootbox": true,
-    "click": true,
-    "waitUntil": true,
-    "getSettledState": true,
-    "count": true,
-    "currentPath": true,
-    "currentRouteName": true,
-    "currentURL": true,
-    "define": true,
-    "Discourse": true,
-    "Ember": true,
-    "exists": true,
-    "File": true,
-    "fillIn": true,
-    "find": true,
-    "Handlebars": true,
-    "hasModule": true,
-    "I18n": true,
-    "invisible": true,
-    "jQuery": true,
-    "keyboardHelper": true,
-    "keyEvent": true,
-    "moduleFor": true,
-    "moduleForComponent": true,
-    "moment": true,
-    "Pretender": true,
-    "QUnit": true,
-    "require": true,
-    "requirejs": true,
-    "RSVP": true,
-    "sandbox": true,
-    "sinon": true,
-    "test": true,
-    "triggerEvent": true,
-    "visible": true,
-    "visit": true,
-    "pauseTest": true
-  },
-  "rules": {
-    "block-scoped-var": 2,
-    "dot-notation": 0,
-    "eqeqeq": [2, "allow-null"],
-    "guard-for-in": 2,
-    "no-alert": 2,
-    "no-bitwise": 2,
-    "no-caller": 2,
-    "no-cond-assign": 0,
-    "no-console": 2,
-    "no-debugger": 2,
-    "no-empty": 0,
-    "no-eval": 2,
-    "no-extend-native": 2,
-    "no-extra-parens": 0,
-    "no-inner-declarations": 2,
-    "no-irregular-whitespace": 2,
-    "no-iterator": 2,
-    "no-loop-func": 2,
-    "no-mixed-spaces-and-tabs": 2,
-    "no-multi-str": 2,
-    "no-new": 2,
-    "no-plusplus": 0,
-    "no-proto": 2,
-    "no-script-url": 2,
-    "no-sequences": 2,
-    "no-shadow": 2,
-    "no-this-before-super": 2,
-    "no-trailing-spaces": 2,
-    "no-undef": 2,
-    "no-unused-vars": 2,
-    "no-with": 2,
-    "semi": 2,
-    "strict": 0,
-    "valid-typeof": 2,
-    "wrap-iife": [2, "inside"]
-  },
-  "parser": "babel-eslint"
+  "extends": "eslint-config-discourse"
 }

package.json

@@ -43,6 +43,8 @@
     "chrome-launcher": "^0.10",
     "chrome-remote-interface": "^0.25",
     "eslint": "^4.19",
+    "eslint-config-discourse": "1.0.5",
+    "install-peerdeps": "^1.10.2",
     "lodash-cli": "https://github.com/lodash-archive/lodash-cli.git",
     "pretender": "^1.6",
     "prettier": "^1.18.2",
@@ -52,6 +54,7 @@
     "sinon": "^7.2.5"
   },
   "scripts": {
-    "preinstall": "node -e \"if(process.env.npm_execpath.indexOf('yarn') === -1) throw new Error('NPM is not supported, please use Yarn instead. ')\""
+    "preinstall": "node -e \"if(process.env.npm_execpath.indexOf('yarn') === -1) throw new Error('NPM is not supported, please use Yarn instead. ')\"",
+    "postinstall": "install-peerdeps --dev eslint-config-discourse -Y --extra-args \"--ignore-scripts\""
   }
 }