There are so many country flag EMOJIs, and 'M-x emoji-insert' does not
show all country flag EMOJIs. Then some country flag EMOJIs can not be
input with emoji-insert. 'M-x emoji-list' conversely show all country
flag EMOJIs, but it is difficult to find a purpose EMOJI from 258
country flag EMOJIs in one group. They should be classified.

I created replacement data following United Nations.
I wanted to place EU flag EMOJI directly under Europe group in parallel
with other regional groups, but emoji-* functions does not support such
data. Then I added 'EU Flag' group with only one EMOJI.

It is better that the data is replaced within #'emoji--generate-file or
#'emoji--parse-emoji-test.