Language hints for PEP 750 template strings

I’ll echo Josh of last year: PEP 750: Tag Strings For Writing Domain-Specific Languages - #19 by thejcannon

Whatever happens here should ideally be applicable as well to non-template strings, so the linters and highlighters and formatters (ideally my YAML formatter also formats the YAML in my Python multiline strings, why shouldn’t they join in the fun?) run on them as well.