Add meta to the directory layout for roles

docsite/rst/playbooks_best_practices.rst

@@ -51,6 +51,8 @@ The top level of the directory would contain files and directories like so::
                 foo.sh        #  <-- script files for use with the script resource
             vars/             #
                 main.yml      #  <-- variables associated with this role
+            meta/             #
+                main.yml      #  <-- role dependencies
 
         webtier/              # same kind of structure as "common" was above, done for the webtier role
         monitoring/           # ""