Consider allowing Punctuated to be indexed with a range

[dtolnay]

Use case from #rust: checking if the segments[..segments.len() - 1] prefix of a Path is equal to some specific prefix.

[Kixiron]

I've also hit a use case where I wanted to remove a variant from an enum, but Punctuated<Variant, Comma> doesn't support .remove(idx)

[dtolnay]

I am not planning to pursue this myself, but if someone else still has this use case, then I would be open to evaluating a PR.