Bookmarks: Add option for custom icon on bookmarks

[stavros-k]

Is your feature request related to a problem? Please describe.
Not exactly, I user NC at work (hosted on my home) to have some notes, etc (makes my life easier).
So we have some internal links that i have bookmarked. Logos are not appear in the bookmarks (because of the internal links)

Describe the solution you'd like
Add option to add custom icons on bookmarks

Describe alternatives you've considered
Leave it as the globe icon, but will have to look the for "name" of the bookmark to find the one i want.

Additional context
Add any other context or screenshots about the feature request here.

[Kippenhof]

It would be nice if you could just have an Button wich allows you to directly select an Image From your Computer/ From your Nextcloud. Sometimes Websites have an Login-Screen, which also makes the Automatic-Screenshot taken of the Site make it look a bit bad.