Add some important hotkeys

[psyGamer]

Ports over the following important hotkeys. The rest will probably follow later
The checklist is just for tracking purposes, not all items need to be completed:

IDK how this would conflict with you wanting to migrate from ReactiveUI.

• Ctrl + Z: Undo
• Ctrl + Shift + Z: Redo
• Ctrl + O: Open File
• Alt + Left: Open Previous File
• Ctrl + Shift + S: Save As
• Ctrl + A: Select All
• Ctrl + W: Select Block
• Ctrl + F: Find Text
• Ctrl + G: Go to Line/Label
• Ctrl + D: Toggle Sending Inputs to Celeste
• Ctrl + Shift + D: Refresh Connection Between Studio and Celeste
• Ctrl + Shift + C: Copy Player Data to Clipboard
• Ctrl + K: Block Comment/Uncomment (line by line processing)
• Ctrl + Shift + K: Block Comment/Uncomment
• Ctrl + P: Remove All Uncommented Breakpoints
• Ctrl + Shift + P: Remove All Breakpoints
• Ctrl + .: Insert/Remove Breakpoint
• Ctrl + Shift + .: Insert/Remove Savestate Breakpoint
• Ctrl + R: Insert room name
• Ctrl + Shift + R: Insert Console Load Command at Current Location and Speed
• Ctrl + Alt + R: Insert Console Load Command at Current Level
• Ctrl + T: Insert Current in-game Time
• Ctrl + L: Combine Consecutive Same Inputs
• Ctrl + Shift + L: Force Combine Inputs Frames
• Ctrl + Down/Up: Go to Comment or Breakpoint
• Ctrl + Left Click on Read/Play Command: Open the read file / Go to the Play Line
• Right Click on Input Area: Show Input Context Menu
• Right Click on Info Area: Show Info Context Menu
• Shift + Mouse Wheel: Tweak Frames Between Selected Input and Mouse Pointed Input
• Ctrl + Shift + Up/Down: Tweak Frames Between Selected Inputs
• Ctrl + Alt + C: Copy File Path
• Alt + Up: Move Selected Lines Up
• Alt + Down: Move Selected Lines Down
• NEW: Alt + R: Reload current file

[swoolcock]

It looks like the Avalonia team really pushes Reactive, so I'll probably just leave it as is.

[swoolcock]

Is this (and the other PR) still relevant?

[psyGamer]

I kinda abandoned AvaloniaTAS