[AIRFLOW-2783][Airflow 2783] Implement eslint for JS code check

Closes apache#3641 from verdan/AIRFLOW-2783-eslint

.rat-excludes

@@ -3,6 +3,8 @@
 .coverage
 .coveragerc
 .codecov.yml
+.eslintrc
+.eslintignore
 .rat-excludes
 requirements.txt
 .*log

CONTRIBUTING.md

@@ -299,3 +299,19 @@ npm run dev
 Should you add or upgrade a npm package, which involves changing `package.json`, you'll need to re-run `npm install` 
 and push the newly generated `package-lock.json` file so we get the reproducible build.
 
+#### Javascript Style Guide
+
+We try to enforce a more consistent style and try to follow the JS community guidelines. 
+Once you add or modify any javascript code in the project, please make sure it follows the guidelines 
+defined in [Airbnb JavaScript Style Guide](https://github.com/airbnb/javascript).
+Apache Airflow uses [ESLint](https://eslint.org/) as a tool for identifying and reporting on patterns in JavaScript,
+which can be used by running any of the following commands.
+
+```bash
+# Check JS code in .js and .html files, and report any errors/warnings
+npm run lint
+
+# Check JS code in .js and .html files, report any errors/warnings and fix them if possible 
+npm run lint:fix
+```
+

airflow/www_rbac/.eslintignore

@@ -0,0 +1,8 @@
+**/*{.,-}min.js
+**/*.sh
+**/*.py
+gantt-chart-d3v2.js
+jqClock.min.js
+coverage/**
+static/dist/*
+static/docs/*

airflow/www_rbac/.eslintrc

@@ -0,0 +1,5 @@
+{
+  "extends": "airbnb-base",
+  "parser": "babel-eslint",
+  "plugins": [ "html" ]
+}