Add support for `templ` syntax

[mfinelli]

I wanted to see about adding support for the templ syntax. It doesn't have many packagecontrol downloads (though I suspect it's because fewer and fewer people use sublime text these days) but Github has support for .templ files so I wanted to see if we could add it anyway. If so I will open a pull request, if not then I will just need to install it locally. Cheers

Syntax:
templ (https://templ.guide / https://github.com/a-h/templ)

Guideline Criteria:
https://packagecontrol.io/packages/Templ%20(go)