Added check for template literals in no-string-refs rule

[jenil94]

This PR aims to fix #2148.

no-string-ref will throw warning when using template literals in string refs.

[ljharb]

Thanks, this seems great.

However, I think it'd be safer if we put this check behind an option, so as to avoid a major change.

[ljharb]

Thanks, this looks great!

It might be nice in a followup PR to make all the attribute cases autofixable :-D