gst-trick-mode.py: add a comment to explain what the code is supposed to do

diff --git a/python/gst-trick-mode.py b/python/gst-trick-mode.py
index e50e252..a01daba 100755 (executable)
--- a/python/gst-trick-mode.py
+++ b/python/gst-trick-mode.py
@@ -1,5 +1,7 @@
 #!/usr/bin/env python
-
+#
+# A simple "trick-mode" player to play a file at a given speed rate.
+#
 # Get a test sample with:
 # youtube-dl -t http://www.youtube.com/watch?v=yWa-YXiSk2Y