Migrate to null-safety about timetable

[JonasWanke]

Migration to null-safety is currently blocked by the following (direct & transitive) dependencies not supporting null safety yet:

• black_hole_flutter: JonasWanke/black_hole_flutter#1
• dartx: simc/dartx#112
• crypto: dart-lang/crypto#105
• time_machine: Dana-Ferguson/time_machine#50

[JonasWanke]

Sorry for the delay and for not keeping this up-to-date. I've recently started the rewrite originally proposed in #17, and as part of this rewrite, also migrated to null-safety and dropped time_machine and dartx dependencies (which wasn't migrated at the time). This rewrite isn't done yet, but I've already managed to overcome the major blockers (visible as layout overflows in the old app).

[JonasWanke]

The work continues, but, unfortunately, quite slowly due to time constraints. I've posted an update here: #17 (comment). I'll try to get the API stable and release a new version very soon. After that, contributions are very welcome!

[JonasWanke]

@IoanaAlexandru As crypto has published a null-safe version two days ago (unblocking dartx) and there's an open PR for time_machine, I'd rather wait for a few more days, hoping we'll be unblocked very soon.

[IoanaAlexandru]

@JonasWanke would it be possible to unsound null safety to do a partial migration, I wonder?

[vendelin8]

dartx seems to be done
black_hole_flutter's PR is closed too
time_machine seems to be abandoned

[mcagrigoktas]

Hi. Does the work continue? Is there anything I can help with