Add page about Android permission handling

## Your Godot version

4.3

## Issue description

in Android, apps have no permissions when first installed, so they have to be enabled first.

every good app
- explains why the app needs certain permissions, so the user knows if they wants to enable that permission
- does not force the user to enable permissions the app needs only for secondary and tertiary features the user does not use

rather than frontliading all permission prompts and refusing to run if even an optional permission is disabled.

to effectively do this, i need methods like these:
- check if a certain permission is enabled
- prompt the user to enable a certain permission

maybe i need more methods i don't suspect, and there may be gotchas i need to know about when designing my permission handling.
this is why i want a documentation page dedicated to all i need to know about Android permission handling.

to understand it, i need this info to be surfaded as a permission handling guide in the documentation, not buried in the class reference

## URL to the documentation page (if already existing)

na