Add Bluespec BH TextMate grammar

[quark17]

Description

Earlier this year, we added Bluespec BH as a language (in the Bluespec group), but there was no TextMate grammar for it, so we pointed to the Haskell grammar, since it's similar and better than nothing. There is now a TextMate grammar for Bluespec BH, so this PR adds that as a submodule (using the add-grammar script) and updates the Bluespec BH record to point to it.

The repo (B-Lang-org/language-bh) is maintained by B-Lang-org, the organization that maintains the open-source BSC compiler. The grammar was adapted from an existing Haskell grammar, with only a few changes so far, but I hope to see more development. If I understand, when Linguist releases are made, the submodules are updated to newer commits; I won't have to submit new PRs to update this submodule.

I am unaware of anything I can run to test the highlighter changes, although I assume that script/add-grammar performed some checks.

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*.FOOBAR+KEYWORDS
  • 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):
      • [URL to each sample source, if applicable]
    • Sample license(s):
  • I have included a syntax highlighting grammar: [URL to grammar repo]
  • I have added a color
    • Hex value: #RRGGBB
    • Rationale:
  • 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: N/A
  • New: https://github.com/B-Lang-org/language-bh

• 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]

LGTM. Thanks.

Note: this PR will not be merged until close to when the next release is made. See here for more details.