Make Music work on mobile

We are trying to make GNOME apps usable in mobile environments. For that, It would be awesome your app can follow the recommendations explained at:

• https://gitlab.gnome.org/GNOME/Initiatives/wikis/GNOME-apps-mobile

Read more about this at the initiative

Current issues (incomplete):

General

• allow for proper display on smaller screensizes: #16 (closed)
• Make SearchBar adaptative. SearchBar is too wide and it's not possible to shrink it. It should be replaced with a HdySearchBar
• The StackSwitcher in the HeaderBar is too wide to fit into 360px. It needs an alternate design. Games has the same issue. See the discussions from https://gitlab.gnome.org/GNOME/gnome-games/issues/80. See the libhandy issue and mockup.

AlbumWidget

• need to solve #13 (closed) first

Player

• needs to be adaptative. See this mockup