Add isEmoji

[MartinSStewart]

I haven't understood what all the unicode categories mean but there doesn't seem to be a way to determine if a unicode character is an emoji. I had a use case for this once where I wanted to find the emoji usage frequency in some messages so I think it would be useful if there was an isEmoji function.

[miniBill]

This involves parsing https://unicode.org/Public/emoji/13.1/emoji-sequences.txt which is... doable but slightly annoying. Will do in the future. Possibly in a couple days

[MartinSStewart]

I agree, that's a strange format to parse. There's no rush though to add this. My use case was for something that I did a few months ago.