language selection popup
WIP: because it's not over yet. WIP because needs !223 (merged)
Strongly recommends !186 (merged) or it will be hard to see and test changes.
Needs https://source.puri.sm/Purism/Systems-Tasks/issues/451 for pipelines.
Left to do:
- specify Debian deps
- position the popover
- clean up commits
- translate and sort language names