Function is_email_link 

pub(crate) fn is_email_link(input: &str) -> bool

Check if the given URL is an email link.

This operates on the raw URL strings, not the linkified version because it gets used in the HTML extractors, which parse the HTML attributes directly and return the raw strings.

Note that LinkFinder::links() is lazy and traverses the input in O(n), so there should be no big performance penalty for calling this function.