Add Templ language

[mtaran]

Adds support for the templ language.

LMK if you'd like more samples or a hint!

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=%28NOT+is%3Afork%29+path%3A%2F.*.templ%24%2F+%2F%5Epackage+%2F+%2F%5Etempl+%5Cw%2B%5C%28%2F
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • https://github.com/emarifer/go-echo-templ-htmx/blob/8442f8ba22a8029ff17d478263cc5426497a875d/views/auth_views/login.templ
    • Sample license(s):
  • I have included a syntax highlighting grammar: https://github.com/templ-go/templ-vscode/blob/main/syntaxes/templ.tmLanguage.json
  • I have added a color
    • Hex value: #dbbd30
    • Rationale: This is the yellow shade used in the language's logo in https://github.com/a-h/templ. The light blue could have been good too, but it seemed too close to the color of Go.
  • I have updated the heuristics to distinguish my language from others using the same extension.

[lildude]

There's already an approved pending PR for this: #6798. That PR will be merged when we're just about to make a new release which happens approximately once a quarter.

Closing as a duplicate.