Add extension creator to the credits page

Given that the credits page now includes many different contributors
(from translators to a list of open source projects used in the
extension), I thought it would be a good idea to add myself too.

Change-Id: Ie098d018e108af7ad2e48906ca75bcb9ec584198
diff --git a/src/css/options.css b/src/css/options.css
index 7190881..3090343 100644
--- a/src/css/options.css
+++ b/src/css/options.css
@@ -191,6 +191,10 @@
   text-align: right;
 }
 
+dialog#credits_dialog .createdby {
+  font-style: italic;
+}
+
 #otheroptions p {
   margin-top: 0;
   margin-bottom: 0;