Register Nextcloud app as a handler for common file types (.pdf/.jpg/.png/.gif/.psd/.txt/.mp4/.ods/.odt/.xls etc.)

### Is your feature request related to a problem? Please describe.
When opening a file from another Android app I want to be able to immediately upload it to my Nextcloud server, but I can't because Nextcloud isn't registered as a handler for files. For example when downloading a PDF bank statement from my banking app I get an "Open with" menu with no Nextcloud option (see screenshot below).

### Describe the solution you'd like
I want the Android Nextcloud app to register itself as a handler for lots of common file types so that I choose it in the "Open with" menu.

### Describe alternatives you've considered
I can't think of any alternatives.

### Additional context