Fix non-matching defaults in docs (#5446) (#5451)

* Allow to pass options as lookup options.

* Adjust tests.

* Fix non-matching defaults.

(cherry picked from commit a978bff2c7)

Co-authored-by: Felix Fontein <felix@fontein.de>

plugins/modules/files/iso_customize.py

@@ -40,6 +40,7 @@ options:
     type: list
     required: false
     elements: str
+    default: []
   add_files:
     description:
     - Allows to add and replace files in the ISO file.
@@ -47,6 +48,7 @@ options:
     type: list
     required: false
     elements: dict
+    default: []
     suboptions:
       src_file:
         description: