Add bpftrace language

[amiremohamadi]

Description

Add bpftrace language.

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*.bt+bpftrace
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • https://github.com/bpftrace/bpftrace/blob/master/tools/syscount.bt
    • Sample license(s): GPL v2 (commit)
  • I have included a syntax highlighting grammar: https://github.com/amiremohamadi/btls/
  • I have added a color
    • Hex value: #ebbe1d
    • Rationale: based on bpftrace's website theme
  • I have updated the heuristics to distinguish my language from others using the same extension.

[lildude]

This is a very popular extension which appears to be use more by languages that are not BPFTrace than BPFTrace according to your search. As such all of those files will now become incorrectly classified.

To prevent this, you will need to find at least another language that uses this extension and meets our usage requirements and add it, along with a heuristic to differentiate the two, as part of this PR.