added blackout mode during presentation

src/ui/src/assets/css/_blackout.scss

@@ -0,0 +1,9 @@
+.blackout {
+	position: absolute;
+	top: 0;
+	left: 0;
+	width: 100vw;
+	height: 100vh;
+	z-index: 1000;
+	background: black;
+}

src/ui/src/models/Mode.js

@@ -0,0 +1,7 @@
+const Mode = Object.freeze({
+	NORMAL   : 1,
+	PRESENT  : 2,
+	BLACKOUT : 3
+});
+
+export default Mode;

src/ui/src/models/Modes.js

@@ -1,6 +0,0 @@
-const Modes = Object.freeze({
-	NORMAL  : 1,
-	PRESENT : 2
-});
-
-export default Modes;