new: added ``charm-resources`` resource declaration shortcut.

bin/compose

@@ -1328,7 +1328,15 @@ get_docker_compose_mixin_from_metadata() {
                     echo "  - $resource:$resource:rw"
                 fi
             done < <(echo "$metadata" | shyaml get-values-0 "host-resources" 2>/dev/null)
-               )
+            while read-0 resource; do
+                if ! [ -e "$CHARM_STORE/$charm/resources$resource" ]; then
+                    err "No '$resource' resource found in ${BLUE}resources/${NORMAL}" \
+                        "directory of charm $DARKYELLOW$charm$NORMAL."
+                    exit 1
+                fi
+                echo "  - $CHARM_STORE/$charm/resources$resource:$resource:rw"
+            done < <(echo "$metadata" | shyaml get-values-0 "charm-resources" 2>/dev/null)
+               ) || return 1
         if [ "$volumes" ]; then
             mixin=$(echo -en "volumes:\n$volumes")
         fi