LibWeb: Give the <blockquote> element some margins in the UA style

Libraries/LibWeb/CSS/Default.css

@@ -143,6 +143,11 @@ basefont {
     display: block;
 }
 
+blockquote {
+    margin-left: 25px;
+    margin-right: 25px;
+}
+
 /* FIXME: I think this should only apply in quirks mode. */
 table {
     text-align: left;