Migrating some files from javascript to typescript (#24663)

* Migrating some files to typescript

* Some other files migrated

* Migrating more javascript to typescript

* Migrating more javascript to typescript

* Fixing types

* Fixing linter errors

* Fixing some imports

* Fixing linter errors

* Renaming the snapshots

* Addressing PR review comments

webapp/channels/package.json

@@ -43,7 +43,7 @@
     "highlight.js": "11.6.0",
     "history": "4.10.1",
     "hoist-non-react-statics": "3.3.2",
-    "html-to-react": "1.5.0",
+    "html-to-react": "1.6.0",
     "inobounce": "0.2.1",
     "katex": "0.16.3",
     "key-mirror": "1.0.1",