*Replace this paragraph with a description of what this PR is changing
or adding, and why. Consider including before/after screenshots.*
*List which issues are fixed by this PR. For larger changes, raising an
issue first helps
reduce redundant work.*
## Pre-launch Checklist
- [ ] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [ ] I signed the [CLA].
- [ ] I read the [Contributors Guide].
- [ ] I updated/added relevant documentation (doc comments with `///`).
- [ ] All existing and new tests are passing.
If you need help, consider asking for advice on the #hackers-devrel
channel on [Discord].
<!-- Links -->
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[CLA]: https://cla.developers.google.com/
[Discord]: https://github.com/flutter/flutter/wiki/Chat
[Contributors Guide]:
https://github.com/flutter/samples/blob/main/CONTRIBUTING.md
* format place_tracker README
* update sentence in README
* sort Dart members, remove unnecessary type declarations
* Run place_tracker on Android and iOS, update project files
* add link to developer preview caveat
* grammar
* update MAINTENANCE
