Buildifier does not support f-strings

Buck2 supports f-string (although [Bazel does not](https://github.com/bazelbuild/starlark/issues/91), at least yet), so it would be nice if `buildifier` did not consider them invalid syntax.

Currently, running it over:

```starlark
name = "Cédric"
print(f"Hello, {name}!")
```

gives

```
> buildifier asdf.bzl
asdf.bzl:2:24: syntax error near "Hello, {name}!"
asdf.bzl # reformat
```

It seems like this could be implemented quite easily similarly to [raw strings](https://github.com/bazelbuild/buildtools/blob/main/build/lex.go#L547), is this correct?

Start in build/lex.go near the raw-string handling linked in the issue, then reproduce the buildifier asdf.bzl example with the provided f-string. Trace how the lexer handles the string and interpolation syntax; done means buildifier accepts the example without a syntax error and formats it successfully.

Written by the indexing model from the issue text.