Client coverage: Mobile and Desktop

[joshtrichards]

Might be valuable to have a broader discussion about whether it's worthwhile centralizing the desktop docs and/or expanding the existing User Manual to incorporate more coverage of the mobile clients. Particularly:

• what, if anything, would be helpful for Android client users (Delete Android user Manual #1583)
• what, if anything, would be helpful for iOS client users (e.g. Question: Nextcloud IOS Documentation #8143)
• what, if anything, would be helpful for desktop client users
• is the existing desktop client documentation something that should be integrated?

Also related: the desktop client manual currently has a completely different look than the docs in this repository. Whether integrated or not, a better user experience would come from using the same theme/settings IMO.

[joshtrichards]

Some updates:

• Desktop docs theme clean/unification(WIP): docs: switch to sphinx_rtd_theme to match other docs desktop#6854
• For the User Manual
  • We should probably document the following for Android:
    • Auto-upload
    • Sync
    • Managing Transfers (Uploads/Downloads)
    • Using the Document Provider