Packer (#172)

* introduce pako and add general packer interface

* add tests for packer

* use function API instead of class API for better tree shaking support

* refcatoring the rollup bundle config

src/index.ts

@@ -8,6 +8,7 @@ export {
   MouseInteractions,
   ReplayerEvents,
 } from './types';
+export { pack, unpack } from './packer';
 
 const { addCustomEvent } = record;