Add mdsvex and Survex data

[mahtaran]

Adds support for the mdsvex language, a Markdown preprocessor for Svelte. At the time of writing, a search returns 4.1k mdsvex files hosted on GitHub: https://github.com/search?type=code&q=NOT+is%3Afork+path%3A*.svx+NOT+%2F%5CA%28%3B%7C%5C*%5B%5E*%5D%2B%24%29%2F

Adds support for the Survex data format, a plaintext data file format used for mapping caves. At the time of writing, a search returns 2.4k Survex data files hosted on GitHub: https://github.com/search?type=code&q=NOT+is%3Afork+path%3A*.svx+%2F%5CA%28%3B%7C%5C*%5B%5E*%5D%2B%24%29%2F

Adds a heuristic to distinguish Survex data and mdsvex files.

Description

No grammar or LSP for mdsvex exists yet. Progress for these is tracked in pngwn/MDsveX#121. For code editors, files can best be marked as Markdown.

No grammar or LSP for Survex data files exists (yet).

Sample for mdsvex is taken from sveltesociety.dev, licenced under the MIT License.

Sample for Survex data is taken from the Philippine Surveys from the BEC expedition 2015, in particular a temporary data file created by Therion during the mapping of the Romeo cave, licenced under the Creative Commons Zero v1.0 Universal licence.

mdsvex colour was chosen to be identical to the primary accent colour of the mdsvex website

Survex data colour was chosen to be identical to the background colour of the navigation bar of the Survex website.

The following RegEx is used to distinguish Survex data files. All files which do not match this are assumed to be mdsvex files.

\A(;|\*[^*]+$)

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*.svx+NOT+%2F%5CA%28%3B%7C%5C*%5B%5E*%5D%2B%24%29%2F
      • https://github.com/search?type=code&q=NOT+is%3Afork+path%3A*.svx+%2F%5CA%28%3B%7C%5C*%5B%5E*%5D%2B%24%29%2F
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • https://github.com/svelte-society/sveltesociety.dev/blob/d2f08cc604a205e51aa8cae3856aae64498096d2/src/routes/recipes/stores/%2Bpage.svx
      • https://github.com/speleo/philippine-surveys-2015/blob/bad0f4490661908bcda3054226ab178bfa799f4a/Romeo/thTMPDIR/data.svx
    • Sample license(s):
      • MIT License
      • Creative Commons Zero v1.0 Universal licence
  • I have included a syntax highlighting grammar
    • mdsvex: no grammar exists yet, progress is tracked in VS Code syntax highlighting? File Type Icon? pngwn/MDsveX#121.
      For code editors, files can best be marked as Markdown (see linked PR).
    • Survex data: no grammar exists (yet).
  • I have added a color
    • mdsvex
      • Hex value: #5f9ea0
      • Rationale: primary accent colour of the mdsvex website
    • Survex data:
      • Hex value: #ffcc99
      • Rationale: background colour of the navigation bar of the Survex website
  • I have updated the heuristics to distinguish my language from others using the same extension.

[lildude]

LGTM. Thanks.

Important

The changes in this PR will not appear on GitHub until the next release has been made and deployed. See here for more details.