wasn't possible in compose 2.0 versions to include the volumes into other files like the services; and
I've kept to the 2.0 version as the extend syntax is removed in 3.0. Reintroduction is being considered. compose-3.0 has a different volume syntax too when migration to 3.0 happens.
…db, metabase
Notes:
extend
syntax is removed in 3.0. Reintroduction is being considered. compose-3.0 has a different volume syntax too when migration to 3.0 happens.closes #134