show CalendarDoor on hover

ui/src/components/calendar/CalendarDoor.vue

@@ -1,8 +1,10 @@
 <template>
   <SVGRect
     style="cursor: pointer"
-    :variant="visible ? 'primary' : undefined"
+    :variant="visible || hovered ? 'primary' : undefined"
     :rectangle="door.position"
+    @mouseover="hovered = true"
+    @mouseout="hovered = false"
   >
     <div class="has-text-danger">{{ door.day }}</div>
   </SVGRect>
@@ -29,5 +31,7 @@ import SVGRect from "./SVGRect.vue";
 export default class extends Vue {
   public door!: Door;
   public visible!: boolean;
+
+  public hovered = false;
 }
 </script>