New jinn-codemirror modes

[timathom]

I'd like to add a new mode to the jinn-codemirror component for syntax highlighting of MARC records. The mode has already been implemented, so I can probably use that and pass in the data with a template expression, but it would be nice to be able to easily extend the jinn-codemirror component.

[JoernT]

This should be moved to the https://github.com/JinnElements/jinn-codemirror repo. I added a feature-request backlinking here.

JinnElements/jinn-codemirror#7 Feel free to comment.