(WIP)feat(frontend): add to favorites

[CarmenPopoviciu]

No description provided.

[teropa]

From a quick glance LGTM.... in theory what you could do to hook up the backend semi-quickly:

1. Create a SelectionControl (or something like that) python widget, that can receive selected items from the frontend.
2. Add a SelectionControl to the display and hook it up to the grid frontend component using the multi-connect API. So that whenever the user favorites a thing, the SelectionControl returns that thing.
3. Make another Buffer for all the selected layouts. It pulls from the SelectionControl.
4. Pull the Buffer into the carousel

[teropa]

@CarmenPopoviciu Shall we close this? We've gone pretty far in the past three months :)

[CarmenPopoviciu]

if @MiguelNicolau thinks we don't want this kind of feature in the future, then yeah, we should