Add KDL language

[zkat]

Description

This PR adds syntax highlighting support for the KDL Document Language. Note: there's two major versions of KDL, 1.0.0 and 2.0.0, with slightly different syntax. This PR includes a TextMate grammar primarily intended for 2.0.0, which is considered the "blessed" version going forward, but which can still highlight 1.0.0 for the most part, since 2.0.0 is mostly forward-compatible as far as anything TextMate would care about.

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*.kdl
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • https://github.com/kdl-org/kdl/blob/main/examples
      • https://github.com/zellij-org/zellij/blob/main/example/default.kdl
      • https://github.com/pop-os/system76-scheduler/blob/a033bf87a7e0ad7a7426baa62f3e41f175dea888/data/config.kdl
      • https://github.com/YaLTeR/niri/blob/main/resources/default-config.kdl
    • Sample license(s):
      • apache-2.0
  • I have included a syntax highlighting grammar: https://github.com/kdl-org/vscode-kdl
  • I have added a color
    • Hex value: #ffb3b3
    • Rationale: It's one of the colors used in the KDL logo (at https://kdl.dev)
  • I have updated the heuristics to distinguish my language from others using the same extension.

[Alhadis]

1. You need to add vscode-kdl as a submodule, which should be done using the script/add-grammar utility:

   $ git rm -rf vendor/grammars/vscode-kdl
   $ ./script/add-grammar https://github.com/kdl-org/vscode-kdl.git

   You appear to have embedded the grammar directly inside Linguist, as opposed to registering it as a submodule.

2. These samples are huge. Please remove the more excessive cases: kdl-schema.kdl, niri.kdl, zellij.kdl, and consider trimming nuget.kdl to no more than 100 lines (which is plenty).

3. You haven't updated languages.yml with a definition for KDL. You'll need to add an entry like the following (making sure the entry precedes the KRL entry):

   Toggle diff

      - justfile
      extensions:
      - ".just"
      ace_mode: text
      language_id: 128447695
   +KDL:
   +  type: data
   +  color: "#FFB3B3"
   +  extensions:
   +  - ".kdl"
   +  tm_scope: source.kdl
   +  ace_mode: tcl
   +  codemirror_mode: yacas
   +  codemirror_mime_type: text/x-yacas
    KRL:
      type: programming
      color: "#28430A"
      extensions:
      - ".krl"
      tm_scope: none
      ace_mode: text
      language_id: 186

   After adding the above entry, run the utility script/update-ids to generate a unique language ID. Do not add one manually.

For more information on adding a new language to Linguist, see CONTRIBUTING.md.

[zkat]

Note: I cut down the niri and zellij files because those are two of the most prominent formats in the community right now, and also are two examples of v1 kdl, so I didn't want to remove them altogether. I can still do it if you'd like and you think there's too many samples right now.

[Alhadis]

Looks good to me. Just one more nit I want to clear up before hitting the big green "Approve" button.

[Alhadis]

LGTM!

@lildude, I've left the popularity metric for you to verify. At a cursory glance, the *.kdl extension appears to be well-established on GitHub.