Use blocked scoped variables

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

src/ol/reproj/common.js

@@ -2,11 +2,11 @@
  * @type {number} Default maximum allowed threshold  (in pixels) for
  *     reprojection triangulation.
  */
-export var ERROR_THRESHOLD = 0.5;
+export const ERROR_THRESHOLD = 0.5;
 
 /**
  * TODO: decide if we want to expose this as a build flag or remove it
  * @type {boolean} Enable automatic reprojection of raster sources. Default is
  *     `true`.
  */
-export var ENABLE_RASTER_REPROJECTION = true;
+export const ENABLE_RASTER_REPROJECTION = true;