Interpreter sees joined and modified emoji as multiple

[r-tae]

(Found while testing #167, but I figured it wasn't specifically pad related)

All of these look like single emoji but break as if they were multiple:

heart, VS16 (this is the regular emoji heart and imo this should definitely work, even if the rest aren't important)
person, ZWJ 🧑‍❤‍🧑
person, skin tone, ZWJ 🧑🏿‍❤‍🧑🏻
person, skin tone 👦🏾

Also this works perfectly fine:

binding to the ZWJ

[kaikalii]

I've made a preliminary fix for this in 540ac08.
Each grapheme will be considered a single character.
I still have some work to do making spans correct, but all your example seem to parse correctly.