Converts github/gemoji#294 (https://raw.githubusercontent.com/github/gemoji/b0193e1063f6f74a774baad5f38c20ad8b7cb59c/db/emoji.json)

Modifications made to input.json

Add united_kingdom and extra flag shortcodes (flag_gb, flag_ps, etc.)

Used in:

https://github.com/Nerimity/nerimity-web/tree/main/src/emoji

Using fork twemoji: https://github.com/Nerimity/twemoji