Position of Gallery-button and inconsistent behavior on hover

[MariusBluem]

Safari-version: 11.0.1
Nextcloud-version: 13.0 beta1

[MorrisJobke]

cc @nextcloud/designers @oparoz

[jancborchardt]

@skjnldsv that #gallery-button needs to be on the far right. Previously that was done via float: right as you can see from gallery/css/gallerybutton.css. How would we do that now with flexbox and the path? The button should definitely not be inthe left cause it interferes with the Add button.

[pixelipo]

It should be done with margin-left:auto, but the problem is that it's always renderer before the Add button.
I think this requires rethinking the JS method responsible for painting the gallery-button

[skjnldsv]

I'll take a look if you want @pixelipo

[skjnldsv]

Please review :) nextcloud/gallery#336 & #7478