Document attributes (#526)

* Add 'acme' action group attribute.

* Compatibility with older ansible-core releases.

* Fix typo.

* Document standard attributes.

* Improve docs.

* Add shortcuts for common combinations.

plugins/modules/certificate_complete_chain.py

@@ -26,6 +26,17 @@ description:
        generated chain is valid, please use C(openssl verify ...)."
 requirements:
     - "cryptography >= 1.5"
+extends_documentation_fragment:
+    - community.crypto.attributes
+attributes:
+    check_mode:
+        support: full
+        details:
+            - This action does not modify state.
+    diff_mode:
+        support: N/A
+        details:
+            - This action does not modify state.
 options:
     input_chain:
         description: