Add Langium Language

[montymxb]

This PR adds language support for the Langium grammar language.

Description

Langium is both the name of the grammar language and the associated language engineering framework (akin in some ways to Xtext, if that rings a bell). Langium grammar files are written and used to generate an associated parser configuration as well as types for the abstract syntax, cross-ref information, and other helpful details.

Altogether it's typically used to generate language implementations with LSP support. Common use cases are building vscode extensions for supporting domain specific languages, syntax highlighting & generation tools.

• I am adding a new language.

  • The extension of the new language is used in hundreds of repositories on GitHub.com.
    • Search results for each extension:
      • ~668 results for *.langium files as of Oct. 27th
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample sources:
      • Mermaid Treemap Grammar (MIT)
      • Zenstack Model Grammar (MIT)
      • Ox Grammar (MIT)
  • I have included a syntax highlighting grammar: [TODO Add highlighting grammar]
  • I have added a color
    • Hex value: #2c8c87
    • Rationale: Color directly pulled from the Langium logo itself (see vscode extension w/ logo)

  - [ ] I have updated the heuristics to distinguish my language from others using the same extension.

The C4 examples is a little long, verging on 1k loc. Let me know if it would be preferable to switch out for something more compact.

[lildude]

The C4 examples is a little long, verging on 1k loc. Let me know if it would be preferable to switch out for something more compact.

Yes please. If the sample is suppressed in the diff, it's too big.

You're also not finished with this PR… you've missed step 4 😉

[montymxb]

Hey @lildude , thanks for the input! Yeah wondered about that too as soon as I was looking at the diff again here (was coming back to something I had sketched up nearly a month ago).

Ahh, whoops! Totally missed that one, thanks for pointing that out. I'll set as draft until both of those are sorted out.

[montymxb]

Both points addressed regarding:

• c4 example (swapped with ox, a minified lox example)
• missing uid