doc: add coding conventions and other rules for PR.

Author: gchoqueux

.eslintrc.js

@@ -74,7 +74,7 @@ module.exports = {
         'max-len': 'off',
         'no-param-reassign': 'off',
         'no-else-return': 'off',
-        'no-var': 'off',
+        'no-var': 'error',
         'vars-on-top': 'off',
         'no-shadow': 'off',
         'no-restricted-properties': 'off',

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,3 +1,7 @@
+## Before contributing
+
+Read [CONTRIBUTING.md](https://github.com/iTowns/itowns/blob/master/CONTRIBUTING.md) and [CODING.md](https://github.com/iTowns/itowns/blob/master/CONTRIBUTING.md) to apply `iTowns` conventions on PRs, Git history and code.
+
 ## Description
 <!--- Describe your changes in detail -->
 

CODING.md

@@ -3,8 +3,16 @@
 iTowns needs `nodejs` (10+) and `npm` (at least 6.x) installed on the system.
 See the [node website](https://nodejs.org) to install node and npm.
 
-## Building
+## Coding
+
+* Search and use existing methods to avoid duplicate code
+* Avoid instance `class/object` in method (optimization with the garbage collector)
+* Give explicite name to constants
+* Avoid duplicate code and encapsulate to simplify
+* For performance reasons, update objects only when needed
 
+## Building
+  
 * Download dependencies: `npm install`
 * Run the dev server:
    * `npm start` (you can change the port: `npm start -- --port 3000`. If you

CONTRIBUTING.md

@@ -120,6 +120,8 @@ Request.
 * If you added third-party libraries, including new version of existing
   libraries, update [LICENSE.md](LICENSE.md). If you plan to add a third-party
   library, start a new issue first.
+* Split the PR if it contains features from different scopes
+* Squash all commits having the same scope
 
 ## IP