LibWeb: Make i, em, address, cite, dfn and var elements italic

Although it is not said that some of the elements need to be italic,
*most* browsers mark them as such to distinguish them from the normal
text, so let's do that too!

Userland/Libraries/LibWeb/CSS/Default.css

@@ -46,6 +46,15 @@ b {
     font-weight: bold;
 }
 
+i,
+em,
+address,
+cite,
+dfn,
+var {
+    font-style: italic;
+}
+
 html,
 address,
 blockquote,