localization for webusb connection failed msg

[jwunderl]

re: microsoft/pxt-microbit#5357

The extension labels would need to be extracted from targetconfig.json and uploaded at build time (along with an rlf if that isn't already there). We do similar things here https://github.com/microsoft/pxt/blob/master/cli/cli.ts#L1852 for gallery, so it'd be walking through all approved extensions, aggregating list of labels, and including in translation. Maybe worth considering packaging in translations for targetConfig.multiplayer.games[?].title as well (suggestion cards underneath multiplayer host screen), since those aren't translatable either right now

[srietkerk]

LGTM! For the extensions label part, do we want to make a new issue or are we just going to continue to reference the issue that you linked?

[jwunderl]

I'm not closing that one with this pr so probably fine to leave it on that one :) Normally I'd just fix it just timing with a vacation / other things to do / bleh