Add playerctl test script

tests/playerctl_script.sh

@@ -0,0 +1,28 @@
+#!/bin/sh
+# This scripts requires playerctl and dbus-send
+
+alias playerctl="playerctl -p my_player "
+
+playerctl metadata
+playerctl play
+playerctl pause
+playerctl play-pause
+playerctl next
+playerctl previous
+playerctl stop
+playerctl position 30
+playerctl position 10-
+playerctl position 10+
+playerctl volume 0.5
+playerctl open "https://testlink.com"
+# TODO: Shuffle and repeat.
+# playerctl shuffle
+# playerctl repeat
+
+# The following are commands not supported by playerctl, thus we use dbus-send
+call() {
+  dbus-send --dest=org.mpris.MediaPlayer2.my_player --print-reply /org/mpris/MediaPlayer2 "$1"
+}
+
+call org.mpris.MediaPlayer2.Raise
+call org.mpris.MediaPlayer2.Quit