Introduce build versions to web app

[jcqli]

We currently don't have build numbers / versions in the web UI, only in Android. We should show a version in the about screen, which can help with formalizing release cuts as well as debugging issues.

Currently needed before we can merge #2014
Open to discussion whether to include it in the Android bug template (context: google/ground-android#2716 (comment))

[jcqli]

@vittorino Do we have designs for something like this?

@gino-m @rfontanarosa Is there a versioning schema that currently exists?

I'd like to get this assigned in the next iteration as it's blocking some tasks that are useful for open source transition

[gino-m]

We've been using the typical major.minor.build versioning in the Android app, it might be a good idea to synchronize at least major and minor web and Android versions so that it's more clear when there might be skew between the two.