docs: Make TOC appear first on narrow screens

This used to put the TOC last, which is the last place you'd want it.

It's not perfect and we do some hacky layoutery to achieve it, but it
should generally be usable.

doc_src/python_docs_theme/static/pydoctheme.css

@@ -241,6 +241,19 @@ dl > dt span ~ em {
         height: auto;
         position: relative;
     }
+    div.sphinxsidebar ul {
+        flex-basis: content;
+        flex-wrap: wrap;
+    }
+    div.sphinxsidebarwrapper {
+        display: flex;
+    }
+    div.sphinxsidebarwrapper > h3:nth-child(5) {
+        display: none;
+    }
+    div#searchbox {
+        display: none !important;
+    }
     div.content {margin-left: 0;}
 
     div.bodywrapper {