Support for PEP 750 a.k.a. "t-strings"

[PEP 750](https://peps.python.org/pep-0750/) is accepted and will be part of Python 3.14(?).

We could add a `html()` function to htpy that takes a t-string and turns it into htpy objects, like `html(t"<div>hi {name}</div>")`. The signature would be `def html(template: Template) -> htpy.Renderable: ...`. Since it returns htpy objects, it could be mixed with "regular" htpy objects.
