function compareSpecificity(a, b) {
	return a.compare(b);
}
Compares two ESQuery selectors by specificity.
@param {ESQueryParsedSelector} a The first selector to compare.
@param {ESQueryParsedSelector} b The second selector to compare.
@returns {number} A negative number if `a` is less specific than `b` or they are equally specific and `a` <= `b` alphabetically, a positive number if `a` is more specific than `b`.