Expo plugin

[KennyHuRadar]

This PR introduces the following:

1. expo plugins for react-native-radar
2. example app that uses continuous native generation that tests correctness of expo plugin. Example app has been bumped to expo SDK 50.
3. updated CI that checks correctness of plugins.

Note: The new example app opts to comment out the code for map libre's dependency and the map. This is due to the fact that there are some issues with the current map-libre's expo plugin. We are opting for our CI to test our code and expo plugin instead of map-libre's. That said, care should be taken when we are updating our RN map UI export and manual QA should be undertaken.

Docs: radarlabs/documentation#451

For this review, there seems to be a lot of lines of code changed but they are mostly auto-generated code from a new expo example app. The files that were modified within the example app are the package.json, app.json, App.tsx and exampleButton.js