refactor: eliminate eslint errors (#920)

* refactor: eliminate eslint errors as many as I can

* refactor: fix more eslint errors in the record module

* LINT: fix @typescript-eslint/unbound-method

* LINT: fix all eslint errors in source code

* LINT: fix as many eslint warnings as possible

Co-authored-by: Justin Halsall <Juice10@users.noreply.github.com>

packages/rrweb/package.json

@@ -78,7 +78,7 @@
     "@xstate/fsm": "^1.4.0",
     "base64-arraybuffer": "^1.0.1",
     "fflate": "^0.4.4",
-    "mitt": "^1.1.3",
+    "mitt": "^3.0.0",
     "rrdom": "^0.1.2",
     "rrweb-snapshot": "^1.1.14"
   }