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/types.ts

@@ -16,7 +16,7 @@ export type URLResource = {
 export type Page = URLResource;
 
 export type ItemType = {
-  filename: string;
+  filename?: string;
   sourceUrl: string;
   replayPrefix: string;
   apiPrefix: string;