Description

Closes #6562

I added Terraform Template as a new markup language. Terraform template files are used to automatically add syntax when given a set of arguments in Terraform. See the Terraform documentation page for more information.

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:
      • ~1.8k search results for the single extension: .tftpl
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • donors.tftpl
      • os_alpine_3_17_userdata.tftpl (removed in 7ce7db6)
      • policy.tftpl
    • Sample license(s):
      • Apache 2.0
      • Apache 2.0
      • MIT
  • I have included a syntax highlighting grammar (uses MPL 2.0)
  • I have added a color
    • Hex value: #7B42BB
    • Rationale: It is one of the purples Hashicorp, the developers of Terraform, officially use for it. The purple in use for the Terraform (AKA "HCL") language is the other purple. It is similar, but noticeably brighter. They have these two official purples listed on in their brand page for Terraform.
  • I have updated the heuristics to distinguish my language from others using the same extension.
    • No other languages use .tftpl, so there is no need.

Misc. Note:

I did list the Terraform Template Language in the HCL group. (HCL is the primary alias for Terraform). This will count it as HCL instead of its own language. I think this is appropriate, but I'm not 100% sure. I'm also not sure if that dismisses the need for a color choice.