Additional notes for devs

CONTRIBUTING.md

@@ -2,6 +2,30 @@
 
 ## Style & Formatting
 * In general, [Prettier](https://prettier.io) is used. See the [Prettier installation and basic instructions](https://prettier.io/docs/en/install.html) for more information.
-* Though you'll see a lot of older style callback code, please utilize modern JavaScript. ES6 classes, arrow functions, and builtins.
+* Though you'll see a lot of older style callback code, please utilize modern JavaScript. ES6 classes, [Arrow Functions](#arrow-functions), and builtins.
 * There is almost never a reason to use `var`. Prefer `const` where you can and and `let` otherwise.
 * Save with UNIX line feeds, UTF-8 without BOM, and tabs set to 4 spaces.
+* Do not include the `.js` suffix when [Importing (require)](#import-require)
+
+### Arrow Functions
+Prefer anonymous arrow functions with access to `this` for callbacks.
+```js
+// Good!
+someApi(foo, bar, (err, result) => {
+    // ...
+});
+
+// Bad :(
+someApi(foo, bar, function callback(err, result) {
+    // ...
+});
+```
+
+### Import (require)
+```javascript
+// Good!
+const foo = require('foo');
+
+// Bad :(
+const foo = require('foo.js');
+```