Add app shortcut keys for switching between Page and Edgeless Mode

[houjoe0829]

• Mac：⌥ + S
• Win：Alt + S
• The information in the settings and shortcut key instructions needs to be updated

How do you think @xell

And I also updated in internal doc about shortcuts

### Tasks
- [x] Add keyboard input support
- [x] Apply keybind style
- [x] Update keybind list

[xell]

My preference would be a combination of ⌥+S for Mac or Alt+S for Win. It's a 2-key shortcut, easy for pressing, and is unique enough to be distinguished with other functions.

[houjoe0829]

My preference would be a combination of ⌥+S for Mac or Alt+S for Win. It's a 2-key shortcut, easy for pressing, and is unique enough to be distinguished with other functions.

Got it, I revised it.

[hwangdev97]

And we need add tooltips for this shortcut:

[danielchim]

I am concerned this may let users who rely on alt key for text input can't able to type specific words, maybe we need to switch to another hotkey?

[hwangdev97]

I think we can address this by offering the functionality to customize keyboard shortcuts.

[xell]

It's done.