My mouse hand was starting to hurt, so I made this. Usage directions:

1. Install the ViolentMonkey browser extension for userscripts.
2. Click the toolbar icon and then click create a new script.
3. Delete everything in the editor and replace it with my code. You can get the code from here. I'll update it at that link if I make changes in future.
4. Change the keybinds at lines 17-22 to suit your preference. Replace the last letter on the line with the letter that you want to press to do the thing.
5. Save.
6. Reload your ChapoChat tabs.

Only tested in Firefox but should hopefully work in anything.

Writing this code is kinda janky and a real pain, hopefully we get official keyboard support soon (hi mods reading this, if you do this, PLEASE make the keys customisable somehow).