Support for import as module, wabac.js 2.20 (#364)

- Extensibility for AWP (customizable toolbar, pass replay iframe messages to parent)
- Support export as module, build separate index.js for module in addition to ui.js
- Update to wabac.js 2.20.0
- bump to 2.2.0

src/appmain.ts

@@ -78,7 +78,7 @@ export class ReplayWebApp extends LitElement {
   swErrorMsg: TemplateResult<1> | string | null = null;
 
   protected swName?: string;
-  private swmanager: SWManager | null;
+  protected swmanager: SWManager | null;
   private useRuffle = false;
 
   private droppedFile: File | null = null;