Maintenance

The compose-go library has to be kept up-to-date with approved changes in the Compose specification. As we define new attributes to be added to the spec, this typically requires:

1. Updating schema to latest version from compose-spec
2. Creating the matching struct/field in types
3. Creating the matching CheckXX method in compatibility
4. If the new attribute replaces a legacy one we want to deprecate, creating the adequate logic in normalize.go