fix(docker-compose.yml): change volumes's name [WiP]

* add volumes: - pgadmin-data:/var/lib/pgadmin
  => pgadmin section

* add pgadmin-data: => volumes:

Before:
docker-compose.yml generate unnamed volume =>
pgadmin

After:
docker-compose.yml generate volume =>
docker-compose-pgadmin-data

To accept this fix:
- remove old docker containers
     docker rm -OLD-
- remove old docker volume
     docker volume rm -OLD-
- run db:start
- run db:migrations:run

Closes VladiRR#24

docker-compose/docker-compose.yml

@@ -25,12 +25,15 @@ services:
     environment:
       PGADMIN_DEFAULT_EMAIL: ${PGADMIN_DEFAULT_EMAIL}
       PGADMIN_DEFAULT_PASSWORD: ${PGADMIN_DEFAULT_PASSWORD}
+    volumes:
+      - pgadmin-data:/var/lib/pgadmin
     restart: unless-stopped
     networks:
       - backend
 
 volumes:
   postgres-data:
+  pgadmin-data:
 
 networks:
   backend: