doc: add border style to content entries

When presenting various directives, roles and more; it can a bit hard
to make a distinction between each content-section when reading
documentation. This help improve the experience, adding a slight border
hint at the top of each content-section.

Signed-off-by: James Knight <[email protected]>

Author: jdknight

doc/_themes/sphinx13b/static/sphinx13b.css

@@ -530,6 +530,13 @@ p.rubric {
     background-color: #efe9e8 !important;
 }
 
+.rst.directive, .rst.role,
+.std.confval, .std.builderval, .std.event,
+.py.function {
+    border-top: 1px solid #ccc;
+    padding-top: 5px;
+}
+
 @media (max-width: 750px) {
     .quick-links {
         display: none;