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

package.json

@@ -59,6 +59,7 @@
   "dependencies": {
     "@types/smoothscroll-polyfill": "^0.3.0",
     "mitt": "^1.1.3",
+    "pako": "^1.0.11",
     "rrweb-snapshot": "^0.7.26",
     "smoothscroll-polyfill": "^0.4.3"
   }