Add attributes to package manager modules (#5954)

Add attributes to package manager modules.

plugins/modules/pkgin.py

@@ -31,6 +31,13 @@ notes:
     - "Known bug with pkgin < 0.8.0: if a package is removed and another
       package depends on it, the other package will be silently removed as
       well.  New to Ansible 1.9: check-mode support."
+extends_documentation_fragment:
+    - community.general.attributes
+attributes:
+    check_mode:
+        support: full
+    diff_mode:
+        support: none
 options:
     name:
         description: