Add keyboard shortcuts to select different modes.

[rev-sin]

Adding keyboard shortcuts would be something I'd love to see help me navigate or select different modes.

My suggestion:

• Num 1-9 for different modes.
• Escape to go back to panning mode.
• Delete key to remove selected states and edges.
• Alt + Enter to edit state features properties.

My references:

• Excalidraw

Can populate more such keyboard shortcuts.