chore(web): unit test re touch CAPS & NCAPS handling

Noting the fiasco here: https://github.com/keymanapp/keyman/pull/6874 & https://github.com/keymanapp/keyman/issues/6910, we should consider adding unit tests to warn us in case it ever breaks again.

I'd estimate a day, tops, to implement it... and even just half a day ought be enough.

It's a matter of 'recording' sequences that produce the bug on affected builds (see #6874's build artifact) and keeping local copies of relevant testing resources available for the unit test engine.