Describe your feature request

Add a method to regex::Captures that is equvalent to (or even just this implementation):

#[inline]
fn full_match(&self) -> Match<'h'> {
    self.get(0).unwrap()
}

Getting the full match is a very common operation, and although the documetation for Regex::get says that getting the result at index 0 will always return Some, that property isn't reflected in the type system. And adding a method like this would expose that guarantee through the type of the public API.