Add hotkeys to tray menu

Rectangle provides hot keys as tray menu items:

Initial work is here (buttons not working currently, needs work): https://github.com/ghokun/RectangleWin/commit/61b2cbe46d1118860b5f4e87360e7942e82ac622

Problems:

• We need to keep track of active window (or latest active window that can be resizable)
• I tried to get process id of current window and compare it with RectangleWin process id. Looks like tray menu returns different process id.

Instead of a endless loop, active window changed hook could be used: https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-setwineventhook?redirectedfrom=MSDN https://stackoverflow.com/questions/4407631/is-there-windows-system-event-on-active-window-changed

That seems a bit excessive. I'd focus on creating a way for configuring the shortcuts.

To be clear, I think clicking on system tray to snap windows is out of scope for this tool as this tool intends to be hotkey-driven.

Fair enough. I am a long time user of rectangle on macos and I always forget some of the bindings (mostly cmd shift and ctrl) because of context switching between multiple OSes during the day. I click the tray icon to quickly remember what it was. Maybe we could add them as readonly items with their current bindings.

I think a UI like the Rectangle's screenshot in its readme where people can go to modify the hotkeys is the most preferable as it's for both learning and modifying.