Move the CodeMirror KCL language support to a package

[mattmundell]

Would you be interested in splitting the language support parts of src/editor/plugins/lsp/kcl/ into a separate JS package?

Benefits:

• other projects can use the language. Eg I wanted to play with KCL in my local CodeMirror.
• if it's structured more like other CM langs then it'll be easier for people to contribute. Eg would make it easier for me to add tests and fix the missing = that is breaking code folding.

I've preped the package: https://github.com/cookshack/codemirror-lang-kcl. If you want to create a repo I'd be keen to make it a PR. It's basically highlight.ts, kcl.grammar and language.ts from kcl/, with the LSP parts stripped out. Also happy to make a PR to integrate the module in modeling-app.