refactor(js): avoid use of window.XXX and move to import/export

- change worker: do not cache html pages (not necessary)
- remove use of window.XXX and maximize import/export,
  this will provide more clarety,
  show circular dependencies + you will benefit IDE help

static/js/app/state.js

@@ -3,7 +3,7 @@
  * Centralized mutable state for app and cached DOM references.
  */
 
-window.app = {
+export const app = {
     currentView: 'grid',
     currentPath: '',
     currentFolder: null,
@@ -29,4 +29,4 @@ window.app = {
     viewFile: null // current file in inline view
 };
 
-window.appElements = {};
+export const appElements = {};