Riot config.json

Copied from https://riot.im/develop/config.json, but modified.

Place to `/home/mikaela/.var/app/im.riot.Riot/config/Riot/config.json`
or `/home/mikaela/.var/app/im.riot.Riot/config/Riot-PROFILENAMEHERE/config.json`

Labs features: https://github.com/vector-im/riot-web/blob/develop/docs/labs.md