Previously emoji like 👨‍👨‍👦 (:man-man-boy:) were decoded as
:man::man::boy: (👨👨👦) even though there is a specific emoji entry for
:man-man-boy:. The solution is to change how the regexp is constructed.
Instead of not setting a sort order for the emoji that go into the
regexp we use reverse alphabetical order to ensure that any emoji that
are inclusive of another (such as :man-man-boy: including :man) get
sorted BEFORE the emoji that they include.

We accomplish this by using a `SortedSet` and implementing `<=>` on `Emoji`