Add Svelte language color

[brunurd]

Description

Svelte language has no color, it support was added without a color, so I add the official branding primary color.

Official brand repo:
https://github.com/sveltejs/branding

Official logo file into sveltejs repo:
https://github.com/sveltejs/branding/blob/master/svelte-logo.svg

Checklist:

• I am associating a language with a new file extension.

  • The new extension is used in hundreds of repositories on GitHub.com
    • Search results for each extension:
      • https://github.com/search?utf8=%E2%9C%93&type=Code&ref=searchresults&q=extension%3AFOOBAR+KEYWORDS+NOT+nothack
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • [URL to each sample source, if applicable]
    • Sample license(s):
  • I have included a change to the heuristics to distinguish my language from others using the same extension.

• 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?utf8=%E2%9C%93&type=Code&ref=searchresults&q=extension%3AFOOBAR+KEYWORDS+NOT+nothack
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • [URL to each sample source, if applicable]
    • Sample license(s):
  • I have included a syntax highlighting grammar: https://github-lightshow.herokuapp.com/
  • I have updated the heuristics to distinguish my language from others using the same extension.

• I am fixing a misclassified language

  • I have included a new sample for the misclassified language:
    • Sample source(s):
      • [URL to each sample source, if applicable]
    • Sample license(s):
  • I have included a change to the heuristics to distinguish my language from others using the same extension.

• I am changing the source of a syntax highlighting grammar

  • Old: https://github-lightshow.herokuapp.com/
  • New: https://github-lightshow.herokuapp.com/

• I am updating a grammar submodule

• I am adding new or changing current functionality

  • I have added or updated the tests for the new or changed functionality.

• I am changing the color associated with a language

  • I have obtained agreement from the wider language community on this color change.
    • [URL to public discussion]
    • [Optional: URL to official branding guidelines for the language]

[lildude]

Unfortunately, you're in for a bit of a struggle. The colour proximity test is failing because the chosen colour is too close to an already used colour and I'm still waiting on GitHub design to allow us to drop the colour proximity requirement. #4506 is tracking other languages which could do with colour correction to align with branding etc.

There's no easy way to find a free colour other than trial and error and repeatedly running the colour proximity test until you find a free colour that isn't too close to an already used colour.

It's also worth pointing out that this won't affect the colours on the language bar as Svelte is grouped under HTML so HTML and its colour are shown in the language bar.

[pietroppeter]

There's no easy way to find a free colour other than trial and error and repeatedly running the colour proximity test until you find a free colour that isn't too close to an already used colour.

In order to pick a new color for Nim, we actually reproduced (in Nim of course) the color-proximity algorithm and you can use this image to pick a valid color (it was run yesterday so it should be up to date):
https://github.com/PMunch/colourfinder

Another image with only valid colors:
https://github.com/Yardanico/random-stuff/blob/master/goodcolours2.png

Only please do not choose anything close to #ffc200, since this is our current proposal (cfr #4900) and we already got the rug pulled under our feet once (see #4866).

[lildude]

The comments on this language colour topic yesterday, and some free time, prompted me to finally do something about it. I've created https://lildude.github.io/linguist-free-colours/ and opened #4903 for feedback.