Add varlink grammar

[fossdd]

Description

https://varlink.org/

Adds varlink grammar and language

systemd started using it (see https://media.ccc.de/v/all-systems-go-2024-276-varlink-now-), so I think it's getting popular

Checklist:

• 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:
      • https://github.com/search?type=code&q=NOT+is%3Afork+path%3A*.varlink
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • https://github.com/varlink/com.redhat.system/blob/master/src/com.redhat.system.varlink
    • Sample license(s):
      • MIT and Apache
  • I have included a syntax highlighting grammar: https://github.com/varlink/language-varlink
  • I have added a color
    • Hex value: #42f1f4
    • Rationale: It's the prefered color of varlink
  • I have updated the heuristics to distinguish my language from others using the same extension.

[lildude]

systemd started using it (see https://media.ccc.de/v/all-systems-go-2024-276-varlink-now-), so I think it's getting popular

With only 51 indexed files, it's got a very long way to go to meet our usage requirements.

[lildude]

Looks like you've still got remnants of a merge conflict that need cleaning up.

[lildude]

Is this really a programming language. Feels more like configuration so would fall under data

[fossdd]

I think it's a markup language as a varlink file describes interfaces (see https://en.wikipedia.org/wiki/Interface_description_language). What do you think?

[lildude]

Markup is for things that result in visual effects, think html. From what I've read, the only varlink files that will be committed are the interface definition files which are data by the fact they're definition files… they're defining the methods the interface implements.

[fossdd]

Thanks for the review! I addressed the issues. Yeah, varlink still isn't used that much (even though it's a few years old now), but I think with systemd adopting varlink it has a pretty good starting point.

[lildude]

The cached licence file needs to be the one generated by the script/add-grammar script you should have used to add the grammar. If you did not use this script, revert your changes and use it and then push your changes. Don't worry about keeping the history clean as we squash all commits when merging.

[lildude]

Whoops.