Give a special "favicon" to the Music App

[rstefko]

So that it can be distinguished when creating an "App" from the URL (on Edge or iPhone etc.). Notes App already has it.

[paulijar]

One thing to notice here is that on Nextcloud, this already happens automatically, provided that the needed PHP extensions are installed. That automatic logic also colors the favicons according the selected color theme. This makes it less attractive to implement an application-side logic for this as it would mostly benefit just ownCloud users (who are nowadays a minority of the user base). And if care is not taken, then it could break the consistency of the favicons on Nextcloud.