Set hover for rows

This makes it easier to pick out the details for each job on the wide
rows.  This is consistent with how other parts of the UI work,
particularly the file selection tab.

Change-Id: I24b3fe029e67f69eea227ba0fd3b95e881151ff1

zuul-results-summary/zuul-results-summary.js

diff --git a/zuul-results-summary/zuul-results-summary.js b/zuul-results-summary/zuul-results-summary.js
index c033ed0..6405083 100644
--- a/zuul-results-summary/zuul-results-summary.js
+++ b/zuul-results-summary/zuul-results-summary.js
@@ -69,6 +69,10 @@
      background-color: var(--background-color-tertiary, #f7ffff);
     }
 
+    tr:hover td {
+     background-color: var(--hover-background-color, #fffed);
+    }
+
     .status-SUCCESS {
       color: green;
     }