Extend justfile file detection

[mkatychev]

Description

Extend justfile filetype detection

As explained on the just repo quickstart:

The search for a justfile is case insensitive, so any case, like Justfile, JUSTFILE, or JuStFiLe, will work. just will also look for files with the name .justfile, in case you'd like to hide a justfile.

the ftdetect in the sactioned justfile vim plugin defines the full globmatch:
https://github.com/IndianBoy42/tree-sitter-just/blob/main/ftdetect/just.vim

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*.just
  • 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?type=code&q=NOT+is%3Afork+path%3A*.FOOBAR+KEYWORDS
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • official justfile examples