Update 'Multiscreen'

Multiscreen.md

@@ -1 +1,22 @@
-Welcome to the Wiki.
+#### Extend display config:
+Tested on RPI4
+```
+{
+    "device": "/dev/dri/card1",
+    "outputs": [
+    {
+        "name": "HDMI1",
+        "virtualIndex": 0
+    },
+    {
+        "name": "HDMI2",
+        "touchDevice": "/dev/input/event1",
+        "virtualIndex": 1
+    }
+  ]
+}
+
+```
+
+for more readings:
+https://doc.qt.io/qt-5.12/embedded-linux.html