Add camera mirroring

Add --video-source=camera, and related options:
 - --camera-id=ID: select the camera (ids are listed by --list-cameras);
 - --camera-size=WIDTHxHEIGHT: select the capture size.

Co-authored-by: Romain Vimont <rom@rom1v.com>
Signed-off-by: Romain Vimont <rom@rom1v.com>

app/scrcpy.1

@@ -75,6 +75,16 @@ Encode the video at the given bit rate, expressed in bits/s. Unit suffixes are s
 
 Default is 8M (8000000).
 
+.TP
+.BI "\-\-camera\-id " id
+Specify the device camera id to mirror.
+
+The available camera ids can be listed by \-\-list\-cameras.
+
+.TP
+.BI "\-\-camera\-size " width\fRx\fIheight
+Specify an explicit camera capture size.
+
 .TP
 .BI "\-\-crop " width\fR:\fIheight\fR:\fIx\fR:\fIy
 Crop the device screen on the server.
@@ -432,6 +442,14 @@ Use a specific MediaCodec video encoder (depending on the codec provided by \fB\
 
 The available encoders can be listed by \-\-list\-encoders.
 
+.TP
+.BI "\-\-video\-source " source
+Select the video source (display or camera).
+
+Camera mirroring requires Android 12+.
+
+Default is display.
+
 .TP
 .B \-w, \-\-stay-awake
 Keep the device on while scrcpy is running, when the device is plugged in.