Add documentation for file uploads on Android

[madsroskar]

Motivation

Currently, it's not clear in our documentation that users need to add configuration for permissions for file uploads on android. Specifically

<uses-permission android:name="android.permission.ACCESS_MEDIA_LOCATION" />

An alternative is to use android:requestLegacyExternalStorage="true" but this is not added by default for expo bare projects, for example

Proposed solution

Add documentation explaining the above