donate: Add UptimeRobot logo

Added a resized version of the original logo, resized to fit better on the page.

Author: grazzolini

sitestatic/uptimerobot_logo.png

@@ -74,6 +74,14 @@ <h3>Commercial sponsors and contributions</h3>
     <img src="{% static "shells_logo.png" %}"
     title="" alt="Shells logo"/></a>
 
+    <p>We would also like to thank <a href="https://uptimerobot.com/"
+    title="UptimeRobot">UptimeRobot</a> for providing their monitoring service to us.
+    UptimeRobot is a leading uptime monitoring service.</p>
+
+    <a href="https://uptimerobot.com/" title="UptimeRobot">
+    <img src="{% static "uptimerobot_logo.png" %}"
+    title="" alt="UptimeRobot logo"/></a>
+
     <h3>Past donors</h3>
 
     <div id="donor-list">