Use blocked scoped variables

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

examples/min-zoom.js

@@ -3,22 +3,22 @@ import View from '../src/ol/View.js';
 import TileLayer from '../src/ol/layer/Tile.js';
 import OSM from '../src/ol/source/OSM.js';
 
-var viewport = document.getElementById('map');
+const viewport = document.getElementById('map');
 
 function getMinZoom() {
-  var width = viewport.clientWidth;
+  const width = viewport.clientWidth;
   return Math.ceil(Math.LOG2E * Math.log(width / 256));
 }
 
-var initialZoom = getMinZoom();
+const initialZoom = getMinZoom();
 
-var view = new View({
+const view = new View({
   center: [0, 0],
   minZoom: initialZoom,
   zoom: initialZoom
 });
 
-var map = new Map({
+const map = new Map({
   layers: [
     new TileLayer({
       source: new OSM()
@@ -29,7 +29,7 @@ var map = new Map({
 });
 
 window.addEventListener('resize', function() {
-  var minZoom = getMinZoom();
+  const minZoom = getMinZoom();
   if (minZoom !== view.getMinZoom()) {
     view.setMinZoom(minZoom);
   }