Provide Compose preview for Play Store listing screens

[jpelgrom]

Summary

Adds Compose previews for screens that are in the Play Store listing, aka the onboarding screen and Wear OS 'scenes' screen.

Screenshots

Link to pull request in Documentation repository

n/a

Any other notes

[dshokouhi]

should we add the updated screenshots to the play folder?

https://github.com/home-assistant/android/blob/master/app/src/full/play/listings/en-US/graphics

Then once we merge this PR we can probably re-push to play store and see if they accept it? Really hope this is why its been rejected.

[JBassett]

should we add the updated screenshots to the play folder?

Yep, everything should be setup so changing those images will cause the play store listing to update as well.

Then once we merge this PR we can probably re-push to play store and see if they accept it? Really hope this is why its been rejected.

Will do once merged!

[jpelgrom]

I've only updated the Wear OS screenshot for now, because the phone preview gives me a much lower resolution than the existing screenshots and it still mostly matches (Google aren't going to complain about font weight I hope?).

Perhaps a future improvement would be to redo all the screenshots with a demo configuration + document the device/emulator so that they can easily be re-done if necessary.