Add Gerrit logo to the intro page

After 12 years of the Gerrit Code Review project
add the logo to the splash page [1] displayed in the
out of the box experience of Gerrit.

By showing the diffy logo on the very first page
the new users see when they first run Gerrit, the
product gives the message of a renewed attention
to the design and user-experience of modern
Gerrit v3.

[1] https://imgur.com/5gpumX8

Change-Id: I6e7085759153c584350ce41e56328298f4f1954c
diff --git a/src/main/resources/static/css/jumbotron.css b/src/main/resources/static/css/jumbotron.css
index 179d408..87c17f8 100644
--- a/src/main/resources/static/css/jumbotron.css
+++ b/src/main/resources/static/css/jumbotron.css
@@ -3,3 +3,10 @@
   padding-top: 50px;
   padding-bottom: 20px;
 }
+
+.gerritlogo {
+  background-image: url(../images/diffy-gerrit-code-review.png);
+  background-size: 400px;
+  background-repeat: no-repeat;
+  padding-left: 450px;
+}
diff --git a/src/main/resources/static/images/diffy-gerrit-code-review.png b/src/main/resources/static/images/diffy-gerrit-code-review.png
new file mode 100644
index 0000000..ff1213c
--- /dev/null
+++ b/src/main/resources/static/images/diffy-gerrit-code-review.png
Binary files differ
diff --git a/src/main/resources/static/intro.html b/src/main/resources/static/intro.html
index 3e61015..39d97e9 100644
--- a/src/main/resources/static/intro.html
+++ b/src/main/resources/static/intro.html
@@ -56,7 +56,7 @@
 
   <!-- Main jumbotron for a primary marketing message or call to action -->
   <div class="jumbotron">
-    <div class="container">
+    <div class="container gerritlogo">
       <h1>Welcome!</h1>
       <p><b><a href="https://www.gerritcodereview.com" target="_blank">Gerrit Code Review</a></b> provides web-based code review and repository
         management for the Git version control system.</p>