add legend styles.

src/DotNetCore.CAP/Dashboard/Content/css/cap.css

@@ -539,4 +539,12 @@ div.metric-null {
 
 .subscribe-table td[rowspan]{
     font-weight:bold;
+}
+
+#legend {
+    background: #f1efef;
+    position: absolute;
+    top: 110px;
+    right: 20px;
+    color: #000;
 }