Add Djot support

[mmibbetson]

This change adds support for the Djot markup language. The grammar used is tree-sitter-djot and the highlights & injections have been adapted for Helix's scopes.

There are 4 highlight queries with TEMP comments above them as they are semantically significant but I don't feel they have appropriate existing scopes.

In preparation for #9458 I will be maintaining a version with inverse precedence.

Closes #12264
Closes treeman/tree-sitter-djot#10

[mmibbetson]

If it would make the reviewing process easier for someone who is unfamiliar with djot, here is an example file. I've had to change the extension to upload it to GitHub so it will need to be changed back to .dj to test the highlights.

Additionally, here are some screenshots demonstrating the highlights:

[zetashift]

Glad to see this, as I enjoy using Djot as well!

I was waiting for treeman/tree-sitter-djot#55 to be merged before starting this PR, but this already looks great to me!

[mmibbetson]

The update to the tree-sitter-djot grammar has been merged in treeman/tree-sitter-djot#56, which includes some breaking changes. It won't be separated into two separate grammars, but the highlights will need to be adjusted regardless.

I'll begin working on the necessary changes today when I get the time.

[mmibbetson]

@zetashift sorry to call you back to this so soon! The highlights and grammar have been updated to the new version of tree-sitter-djot. Could we maybe get this PR marked with the S-waiting-on-review label?

#9458 has been merged, so I'll also need to swap out the queries to be inverse. I've already maintained that change separately so I'll just quickly make that adjustment later today.