Add the rotate command & button

[daonb]

What's missing? Please describe your flow and where this feature will help.
Sometimes I start in full screen and I use a layout:

┌────────────┬────────┐
│            │        │
│            │        │
│            │        │
│     A      │   B    │
│            │        │
│            │        │
│            │        │
└────────────┴────────┘

Than I switch to a narrow view and I want them to be on top to each other:

┌─────────┐
│         │
│         │
│    A    │
│         │
│         │
├─────────┤
│         │
│    B    │
│         │
│         │
└─────────┘

I want a rotate botton between the split button that will rotate the layout
90 degrees clock wise. Pressing the button twice will restore the original layout
but with B on the left and A on the right which is also usefull at times.

Additional Context

There should be a new command rotate which the new button runs.
The Layout class in src/layout.ts is the place to start.