Make cheatsheet more robust

[AndreasArvidsson]

We had user that disabled a spoken form in the csv file which broke our cheatsheet

 > user.private_cursorless_cheat_sheet_show_html()
KeyError: 'applyFormatter'

Since we actually instruct people how to do that in our docs this needs to be made more robust.
https://www.cursorless.org/docs/user/customization/#example-of-custom-formatter-command

There's also a question if we actually want to read from the Talon registry or if we should read from the same data structure that constructs the spoken form json file?