Use blocked scoped variables

In addition to using const and let, this also upgrades our linter config and removes lint (mostly whitespace).

examples/simple.js

@@ -4,7 +4,7 @@ import TileLayer from '../src/ol/layer/Tile.js';
 import OSM from '../src/ol/source/OSM.js';
 
 
-var map = new Map({
+const map = new Map({
   layers: [
     new TileLayer({
       source: new OSM()