[MISC] Add build instructions in Compose

pica-db-backup-rotation/docker-compose.yml

pica-db-backup/docker-compose.yml

pica-etherpad-db/CHANGELOG.md

pica-etherpad-db/Dockerfile

pica-etherpad-db/README.md

pica-etherpad-db/config/binary_log.cnf

pica-etherpad-db/config/myisam_perf.cnf

pica-lufi/README.md

pica-lufi/docker-compose.yml

pica-mattermost/docker-compose.yml

pica-metrics-bot/docker-compose.yml

pica-mumble-web/docker-compose.yml

pica-nextcloud/docker-compose-cet.yml