Add Phel language

[JesusValera]

Add Phel programming language to linguist.

Issue: https://github.com/phel-lang/phel-lang/issues/158

Description

There are more than 180 files in Github using the .phel extension and some projects were created from scratch like

• https://github.com/mabasic/mariobasic-n7
• https://github.com/Chemaclass/phel-snake

Checklist:

• [x] I am adding a new language.
  • [x] The extension of the new language is used in hundreds of repositories on GitHub.com.
    • Search results for each extension:
      • https://github.com/search?q=path%3A*.phel&type=code
  • [x] I have included a real-world usage sample for all extensions added in this PR:
    • https://github.com/JesusValera/linguist/blob/add-phel-language/samples/Phel/sample.phel
    • Sample license(s):
  • [ ] I have included a syntax highlighting grammar.
  • [ ] I have updated the heuristics to distinguish my language from others using the same extension.

The last two points are not selected because, it uses a Common Lisp grammar & the extension is unique (.phel).

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Please, let me know if something is missing, glad to keep improving the PR if necessary!