Document launchers in virtual displays

Mention how to start a launcher in a virtual display.

Refs #5592 <#5592>

Author: rom1v

doc/virtual_display.md

@@ -15,21 +15,38 @@ scrcpy --new-display=/240    # use the main display size and 240 dpi
 
 On some devices, a launcher is available in the virtual display.
 
-When no launcher is available, the virtual display is empty. In that case, you
-must [start an Android app](device.md#start-android-app).
+When no launcher is available (or if is explicitly disabled by
+[`--no-vd-system-decorations`](#system-decorations)), the virtual display is
+empty. In that case, you must [start an Android
+app](device.md#start-android-app).
 
 For example:
 
 ```bash
 scrcpy --new-display=1920x1080 --start-app=org.videolan.vlc
 ```
 
+The app may itself be a launcher. For example, to run the open source [Fossify
+Launcher]:
+
+```bash
+scrcpy --new-display=1920x1080 --no-vd-system-decorations --start-app=org.fossify.home
+```
+
+[Fossify Launcher]: https://f-droid.org/en/packages/org.fossify.home/
+
+
 ## System decorations
 
-By default, virtual display system decorations are enabled. But some devices
-might display a broken UI;
+By default, virtual display system decorations are enabled. To disable them, use
+`--no-vd-system-decorations`:
+
+```
+scrcpy --new-display --no-vd-system-decorations
+```
 
-Use `--no-vd-system-decorations` to disable it.
+This is useful for some devices which might display a broken UI, or to disable
+any default launcher UI available in virtual displays.
 
 Note that if no app is started, no content will be rendered, so no video frame
 will be produced at all.