command: add video-stereo-mode property

Enables runtime change of the option.

Fixes #2994.

DOCS/man/input.rst

@@ -1851,6 +1851,9 @@ Property list
 ``video-rotate`` (RW)
     See ``--video-rotate`` option.
 
+``video-stereo-mode`` (RW)
+    See ``--video-stereo-mode`` option.
+
 ``seekable``
     Return whether it's generally possible to seek in the current file.
 

player/command.c

@@ -3737,6 +3737,7 @@ static const struct m_property mp_properties[] = {
     {"af", mp_property_af},
 
     {"video-rotate", video_simple_refresh_property},
+    {"video-stereo-mode", video_simple_refresh_property},
 
     {"ab-loop-a", mp_property_ab_loop},
     {"ab-loop-b", mp_property_ab_loop},