Ability to raise windows from custom layout

[tmandry]

Hey there, I decided to give Amethyst a spin since I saw you landed custom layouts, and I'm liking it. I think the custom layout stuff looks really promising and Javascript was a good choice.

Is your feature request related to a problem? Please describe.

A custom layout might want the ability to raise a window outside the normal order. For example, you want to move to a window in an adjacent column without cycling through. This becomes more important when windows are sharing the same frame, because a user might want to keep the current top window.

Describe the solution you'd like

getFrameAssignments could support an optional topMost key or similar that causes that window to be raised.

This would ideally take an array of window IDs which would be raised in order (so last window ends up with the focus). This would be useful e.g. for flipping through "pages" of windows.

Describe alternatives you've considered

I tried implementing my own window manager, but it's more complexity than I care to maintain :)

Additional context

For this to be as useful as possible you probably also need the ability to define >4 commands. An API for defining named commands for each layout would be nice, but I know it's early days.