docs RDT theme: fix bottom margin of lists items

List items with two ore more blocks are not well rendered. E.g. the gap
between last block (l1-b2) of the first list item and the following list
item (L2) is to small::

    * L1 xxxxxxxxxx
      xxxxxxxxxxxxx

      l1-b2 xxxxxxx
      xxxxxxxxxxxxx
    * L2 xxxxxxxxxx
      xxxxxxxxxxxxx

So that it can be read more liquidly, a distance was added to the last
block (l1-b2)::

    * L1 xxxxxxxxxx
      xxxxxxxxxxxxx

      l1-b2 xxxxxxx
      xxxxxxxxxxxxx

    * L2 xxxxxxxxxx
      xxxxxxxxxxxxx
Signed-off-by: NMarkus Heiser <markus.heiser@darmarit.de>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/sphinx-static/theme_overrides.css

@@ -56,6 +56,12 @@
 	font-family: "Courier New", Courier, monospace
     }
 
+    /* fix bottom margin of lists items */
+
+    .rst-content .section ul li:last-child, .rst-content .section ul li p:last-child {
+          margin-bottom: 12px;
+    }
+
     /* inline literal: drop the borderbox, padding and red color */
 
     code, .rst-content tt, .rst-content code {