fix: jest setup was voiding custom turbo mocks

[DoctorJohn]

Description

This PR updates the jest.setup.ts file to make it suitable to be used by projects using the rn google mobile ads library. The docs are updated accordingly.

I made sure we only mock our own native modules in the jest.setup.ts file so the mocks won't interfere with other libraries' or custom mocks.

Related issues

• Fixes [🐛] Jest Setup file is deleting TurboModuleRegistry.get, breaking test suites #631

Checklist

• I read the Contributor Guide
  and followed the process outlined there for submitting PRs.
  • Yes
• My change supports the following platforms;
  • Android
  • iOS
• My change includes tests;
  • e2e tests added or updated in __tests__e2e__
  • jest tests added or updated in __tests__
• I have updated TypeScript types that are affected by my change.
• This is a breaking change;
  • Yes
  • No

Test Plan

• I successfully used the updated jest.setup.ts file via setupFiles in one of my projects (before I used custom mocks for this library)
• I made sure yarn tests:jest still passes all tests just like before after I removed the Platform mock

[docs-page]

To view this pull requests documentation preview, visit the following URL:

docs.page/invertase/react-native-google-mobile-ads~636

Documentation is deployed and generated using docs.page.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 43.11%. Comparing base (a34c7ba) to head (8e22af6).
Report is 56 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #636      +/-   ##
==========================================
- Coverage   43.72%   43.11%   -0.60%     
==========================================
  Files          30       31       +1     
  Lines         549      573      +24     
  Branches      151      153       +2     
==========================================
+ Hits          240      247       +7     
- Misses        309      326      +17