Add actions to resize panels

[yoRyuuuuu]

I'd like to propose adding actions to resize panels such as the terminal, assistant, and project panels.

I understand that you can currently resize panels using the vim::ResizePaneUp action, but that only works when Vim mode is enabled.

So, I'd like to propose adding actions to resize these panels that can be used regardless of whether Vim mode is active.

If this sounds good, I'd be happy to implement this feature myself.