📝 Document nested node addition with "_" in xml module (#2371) (#2426)

* 📝 Document nested node addition with "_" in xml module

Nested node addition using "_" to indicate sub nodes, and attributes are only documented in tests and issues, where is hard to find.

* 🚨 Fix trailing space

* Apply suggestions from code review

Add missing collection prefix for modules.

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

* Add missing comments

* Update xml.py

* Fix linter warnings

Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit 4b0d2dcfe0)

Co-authored-by: Daniel-Sanchez-Fabregas <33929811+Daniel-Sanchez-Fabregas@users.noreply.github.com>

plugins/modules/files/xml.py

@@ -285,6 +285,22 @@ EXAMPLES = r'''
       z: http://z.test
     attribute: z:my_namespaced_attribute
     value: 'false'
+
+- name: Adding building nodes with floor subnodes from a YAML variable
+  community.general.xml:
+    path: /foo/bar.xml
+    xpath: /business
+    add_children:
+      - building:
+          # Attributes
+          name: Scumm bar
+          location: Monkey island
+          # Subnodes
+          _:
+            - floor: Pirate hall
+            - floor: Grog storage
+            - construction_date: "1990"  # Only strings are valid
+      - building: Grog factory
 '''
 
 RETURN = r'''