Update outdated cloud-functions-angular example

[rohitmanokaran]

cloud-functions-angular is the only firebase example using angular and typescript. The versions of all the tools (eg. angular2) used in it however are very out of date.

A codelab used to exist at https://github.com/firebase/codelab-friendlychat-web/blob/main/cloud-functions-angular that the README files in the example lead to. The url is now non existent, but what looks like a copy of the old codelab is available at https://kiosk-dot-codelabs-site.appspot.com/codelabs/firebase-cloud-functions-angular/index.html?index=..%2F..index#0.

• Update the examples to the latest version of the tools.
• Add the codelab on the website again so the README file links work once the example is updated.

[rohitmanokaran]

Created https://github.com/firebase/codelab-friendlychat-web/pull/647 to fix the example code.