Add Custom URL Scheme for Launching Nextcloud App from Another apps

### Is your feature request related to a problem? Please describe.
It is trying to call the Nextcloud application directly from another application, but it cannot call it directly like nextcloud://, because the URL custom scheme is not set. It's only set up for http and https.

### Describe the solution you'd like
https://github.com/nextcloud/android/blob/master/src/main/AndroidManifest.xml
How about adding an intent-filter to Manifest.xml above so that it can be called with nextcloud:// ?

I think that the Nextcloud application should only be launched and there is no need to open the Nextcloud application with Deep link.