Add --list-displays

Add an option to list the device displays properly.

app/data/bash-completion/scrcpy

@@ -19,6 +19,7 @@ _scrcpy() {
         -K --hid-keyboard
         -h --help
         --legacy-paste
+        --list-displays
         --list-encoders
         --lock-video-orientation
         --lock-video-orientation=

app/data/zsh-completion/_scrcpy

@@ -26,6 +26,7 @@ arguments=(
     {-K,--hid-keyboard}'[Simulate a physical keyboard by using HID over AOAv2]'
     {-h,--help}'[Print the help]'
     '--legacy-paste[Inject computer clipboard text as a sequence of key events on Ctrl+v]'
+    '--list-displays[List displays available on the device]'
     '--list-encoders[List video and audio encoders available on the device]'
     '--lock-video-orientation=[Lock video orientation]:orientation:(unlocked initial 0 1 2 3)'
     '--max-fps=[Limit the frame rate of screen capture]'