Add regional indicator symbols to emoji picker

[robintown]

https://en.wikipedia.org/wiki/Regional_indicator_symbol

While they aren't technically meant to be used as emoji, it is quite common for them to be used this way. For example, users on other (bridged) platforms will react with regional indicators to spell out words, and I would like to be able to do the same from Element. They are already present in Emojibase, they just don't currently show up in the emoji picker.

[robintown]

oops, dup of #14963