add unscheduled task to user guide

Author: Archaeopteryx

ui/userguide/UserGuideBody.jsx

@@ -66,6 +66,10 @@ const notations = [
     classes: 'btn-yellow ug-btn-yellow',
     explanation: 'Yellow, unknown',
   },
+  {
+    classes: 'btn-unscheduled ug-btn-bg',
+    explanation: 'Turquoise, unscheduled',
+  },
   {
     classes: 'btn-ltblue ug-btn ug-btn-bg',
     explanation: 'Light blue, superseded',