Add docs for ansible-core 2.13 use (#4202) (#4586)

* Add docs for ansible-core 2.13 use

local testing shows fine, adding here as example for other filters/tests

* Update plugins/filter/random_mac.py

* Improve docs.

* Remove wrong 'positional'.

Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit e62a56e15c)

Co-authored-by: Brian Coca <bcoca@users.noreply.github.com>

plugins/filter/random_mac.py

@@ -20,6 +20,35 @@
 from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type
 
+DOCUMENTATION = '''
+  name: random_mac
+  short_description: Generate a random MAC address
+  description:
+    - Generates random networking interfaces MAC addresses for a given prefix.
+  options:
+    _input:
+      description: A string prefix to use as a basis for the random MAC generated.
+      type: string
+      required: true
+    seed:
+      description:
+        - A randomization seed to initialize the process, used to get repeatable results.
+        - If no seed is provided, a system random source such as C(/dev/urandom) is used.
+      required: false
+      type: string
+'''
+
+EXAMPLES = '''
+- name: Random MAC given a prefix
+  debug:
+    msg: "{{ '52:54:00' | community.general.random_mac }}"
+    # => '52:54:00:ef:1c:03'
+
+- name: With a seed
+  debug:
+    msg: "{{ '52:54:00' | community.general.random_mac(seed=inventory_hostname) }}"
+'''
+
 import re
 from random import Random, SystemRandom