Support for newer Unicode versions.

[jiri]

Currently, new emoji introduced in later unicode versions aren't supported. This can be fixed by either manually updating the conversion table or better yet, fetching it automatically from somewhere.

[vbatts]

I'm working to ensure https://github.com/emojisum/emojisum has 256 of the most common, distinct emojis and emojisum/emojisum#5 points out some emoji that are not provided by rust-emojicons. Would love to see the maps available here!

[vbatts]

https://github.com/emojisum/emojisum/blob/master/emoji/list.md has the latest generate list.