Use blocked scoped variables

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

src/ol/tilegrid/common.js

@@ -1,9 +1,9 @@
 /**
  * @type {number} Default maximum zoom for default tile grids.
  */
-export var DEFAULT_MAX_ZOOM = 42;
+export const DEFAULT_MAX_ZOOM = 42;
 
 /**
  * @type {number} Default tile size.
  */
-export var DEFAULT_TILE_SIZE = 256;
+export const DEFAULT_TILE_SIZE = 256;