Add brewfile to bootstrap

[bval]

I have added a Brewfile and invoked brew bundle inside the app's script/bootstrap as a convenience to other developers.

Description

While cloning linguist to develop against it, I noticed that it lacks a Brewfile and an invocation of brew bundle in the script/bootstrap file, which would alleviate the need for manually installing all of the dependencies. I have added this to better automate and document the dependencies. I have also added a test for whether the user is running on macOS to the potential invocation of this new functionality.

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: [URL to grammar repo]
  • 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: [URL to grammar repo]
  • New: [URL to grammar repo]

• 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]

[Alhadis]

IMHO, this isn't any more convenient than simply copying the brew install commands from CONTRIBUTING.md and pasting them into the terminal. If anything, it's adding needless complexity to a step that contributors are only expected to run once.

[rick]

This conforms to "scripts to rule them all", which is still very much a standard at GitHub and with various GitHub open source projects. 👍

[rick]

ship this automation