Create custom syntax highlighting rules for kbdx

[srithon]

Currently, the TOML syntax highlighting on GitHub is flagging all of the unquoted rvalues red, as they would not be valid TOML syntax.

This is valid syntax in kbdx, so we need to add custom rules to make sure our documents get highlighted properly.
Another issue that could come about is tap macro syntactic sugar being interpreted as comments, since they are prefixed with a hash symbol.
This is currently being masked by the red highlighting from the first issue, but after that is fixed it will likely become a problem.
Custom highlighting rules would fix both of these

[srithon]

Update: I changed the base language we use from toml to ini, which renders a lot better on GitHub. It would still be cool to have a custom syntax highlighter for this, but it's less urgent now.