[Talk-ko] promote mailinglist in ID

[Max]

After submitting a changeset ID shows on the left side some ways to get 
in touch with the community. This list is defined in a github.
Currently the Telegram Supergroup is promoted there while this official 
mailinglist is lacking.

https://github.com/osmlab/osm-community-index/tree/master/resources/asia/korea

Since they ask for a contact email address, I suppose Andrew Errington 
should file an issue
https://github.com/osmlab/osm-community-index/issues/new


m.