[notifications] autogenerate package documentation

[Simek]

Why

Fixes ENG-6985

expo-notifications is the latest package which left to be migrated to autogenerated docs, let's finally close the migration process.

How

As always, the documentation content has been moved to the package source. There were few small type changes (mainly extractions) required for proper docs data extraction by TypeDoc.

Additionally, I need to add new APISection feature which allows organizing content (currently method only to be precise) in custom sections, which can be manually ordered and are placed before general API section. This was required to mimic the current structure of the page.

I have also updated the API docs section in our contributing guide to address newly added @header parameter.

Test Plan

The new doc page has been tested by running docs app locally.

Package tests and lint do not yield any errors.

Preview

Checklist

• Documentation is up to date to reflect these changes (eg: https://docs.expo.dev and README.md).
• Conforms with the Documentation Writing Style Guide
• This diff will work correctly for expo prebuild & EAS Build (eg: updated a module plugin).

[linear]

ENG-6985 Notifications

[amandeepmittal]

One small suggestion but it shouldn't be blocking this PR (and I think its unrelated to the changes of this PR).

Thanks for moving these docs to be autogenerated!