Please could you export `SchemeType` or add `is_special()` method to `Url`

[samuelcolvin]

Currently there's no way to check if a url/scheme is "special" without duplicating logic from

rust-url/url/src/parser.rs

Lines 161 to 167 in 1c1e406

	pub fn from(s: &str) -> Self {
	match s {
	"http" | "https" | "ws" | "wss" | "ftp" => SchemeType::SpecialNotFile,
	"file" => SchemeType::File,
	_ => SchemeType::NotSpecial,
	}
	}

Would be great if this could be made public, or an is_special method added to Url.

Also, I guess SchemeType::from should probably be implemented via the Into trait?

[qsantos]

See #826