Show GeckoView version on About page

[cpeterso]

We should display both the Focus app version and GeckoView's Gecko version on Focus's About page, including Gecko's build ID or date. This information will be helpful when people report Gecko-related bugs in Focus.

[ekager]

Note - we are adding a focus:debug page #1655 which may be a better place for engine info. There is a PR #2089 open.

[cpeterso]

The following bug will add GeckoView version information to the GeckoRuntime:

https://bugzilla.mozilla.org/show_bug.cgi?id=1465939

[ekager]

I added a quick fix for this, grabbing the version from gradle and adding it to BuildConfig, but keeping this open for when information is in GeckoRuntime.

[cpeterso]

This bug probably doesn't need to block the Focus 7.0 milestone because Emily has a workaround and few users will need to know their GeckoView version. :)

[pocmo]

Don't we display the GeckoView version on the about page already?

[bbinto]

Alright, let's close this issue!