CI: Manifest V2 being deprecated in Chrome

[adomasven]

We have deployed a MV3 Zotero Connector for Chrome now. However, it has certain incompatibilities with the MV2 architecture, mainly, the translation is run in a sandboxed iframe on a document that is DOMParsed (i.e. not live). This means that certain things like clicking on elements doesn't work.

It's likely that Edge translation will switch to that at some point too, meanwhile its not clear right now whether we will be able to maintain the current architecture where translation runs on page or not on Firefox, but Firefox currently doesn't have plans to deprecate MV2, which we will also continue using while available.

Given all of the above, it's not clear what to do for CI on this repo going forward. The new Chrome MV3 Connector is likely to have translation test failures on websites where the old and soon to be unavailable MV2 Connector does not. There may be some rationale to run CI on both Firefox and Chrome, including to be able to catch translation issues better.

[alex-ter]

There may be some rationale to run CI on both Firefox and Chrome, including to be able to catch translation issues better.

FWIW I think this approach would make sense and is even more important given the MV2 vs 3 differences.