Add .vs GLSL vertex shader extension

[FrostKiwi]

Added missing .vs extension to recognize .vs files as GLSL.
For GLSL fragment shaders it is common to have either .fs or .frag as your file extension. Both are present in this line of languages.yml. For the vertex shader however, only .vert is present and the counterpart to .fs, .vs has been forgotten. This has been fixed with this PR

Description

This solves GitHub support ticket #2320418, which had the following issue:

Issue caused by .vs not being in linguist

The main GitHub website does Syntax Highlighting based on the language it detects. It also shows a repo's language breakdown:

This feature has a bug when detecting GLSL Shaders. You can observe this bug in my repo: https://github.com/FrostKiwi/Mirrorball
Take a look at the detected GLSL shaders: https://github.com/search?q=repo%3AFrostKiwi%2FMirrorball++language%3AGLSL&type=code and what is actually in that directory: https://github.com/FrostKiwi/Mirrorball/tree/main/src/shd

You see two file types.

• The GLSL Fragment Shaders with a .fs file extension.

  • File type properly detected as GLSL and syntax highlighting present:
    

• The GLSL Vertex Shaders with a .vs file extension

  • File type not properly detected as GLSL and no syntax highlighting present:
    
  • Furthermore, these files are not listed in the Language breakdown: https://github.com/search?q=repo%3AFrostKiwi%2FMirrorball++language%3AGLSL&type=code

.fs for fragment shaders and .vs for vertex shaders are a common choise along side .frag and .vert. So this is not a repo-specific naming, but a common one.

Checklist:

• I am adding a new extension to a language.
  • The new extension 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*.vs
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s) (Note the missing syntax highlighting of .vs files, but all .fs in those same repos have it):
      • https://github.com/google/filament/blob/d11a782c3e73ce705395682ad7503ddd9f5d9f74/shaders/src/main.vs#L4
        • Included as a sample. From Google's filament repo: https://github.com/google/filament Licensed under Apache License 2.0 Licence file
      • https://github.com/FrostKiwi/Mirrorball/blob/main/src/shd/project.vs
        • Included as a sample. File from repo https://github.com/FrostKiwi/Mirrorball under the MIT licence Licence file
      • https://github.com/RandyGaul/cute_headers/blob/265f675325629f3bae5710c6f1362bba9f619357/examples_cute_gl_and_c2/simple.vs#L4
  • I have included a change to the heuristics to distinguish my language from others using the same extension.
    • Not necessary, already present for GLSL and .vs is unique to GLSL, at least in linguist.

[lildude]

Please add the samples you've referenced in the template to the PR in the GLSL samples directory and update the template to state the licence of each file. ProTip: if the file is not shown fully in the diff, it's too big so should be replaced with a smaller file. Two samples should be plenty so pick two that differ the most (these are used to train the classifier).

Please also update the search query in the template.

[FrostKiwi]

Please add the samples you've referenced in the template to the PR in the GLSL samples directory and update the template to state the licence of each file. ProTip: if the file is not shown fully in the diff, it's too big so should be replaced with a smaller file. Two samples should be plenty so pick two that differ the most (these are used to train the classifier).

Please also update the search query in the template.

Updated to reflected the requested changes.