Bind AudioStreamInteractive TRANSITION_TO_TIME_PREVIOUS_POSITION

In C++, enum AudioStreamInteractive::TransitionToTime has three "real"
members, plus MAX. Previously only TRANSITION_TO_TIME_SAME_POSITION and
TRANSITION_TO_TIME_START were bound for GDScript. But
TRANSITION_TO_TIME_PREVIOUS_POSITION can be set via the editor, so can
easily appear in an AudioStreamInteractive resource without needing to
drop down to C++. I can't see anything to suggest that it was
deliberately not exposed.

Bind this enum member. Add documentation.

Co-authored-by: A Thousand Ships <96648715+AThousandShips@users.noreply.github.com>

modules/interactive_music/audio_stream_interactive.cpp

@@ -522,6 +522,7 @@ void AudioStreamInteractive::_bind_methods() {
 
 	BIND_ENUM_CONSTANT(TRANSITION_TO_TIME_SAME_POSITION);
 	BIND_ENUM_CONSTANT(TRANSITION_TO_TIME_START);
+	BIND_ENUM_CONSTANT(TRANSITION_TO_TIME_PREVIOUS_POSITION);
 
 	BIND_ENUM_CONSTANT(FADE_DISABLED);
 	BIND_ENUM_CONSTANT(FADE_IN);

modules/interactive_music/doc_classes/AudioStreamInteractive.xml

@@ -199,6 +199,9 @@
 		<constant name="TRANSITION_TO_TIME_START" value="1" enum="TransitionToTime">
 			Transition to the start of the destination clip.
 		</constant>
+		<constant name="TRANSITION_TO_TIME_PREVIOUS_POSITION" value="2" enum="TransitionToTime">
+			Transition to the last played position in the destination clip, if there was a previous transition from that clip. Otherwise, plays from the start of the destination clip.
+		</constant>
 		<constant name="FADE_DISABLED" value="0" enum="FadeMode">
 			Do not use fade for the transition. This is useful when transitioning from a clip-end to clip-beginning, and each clip has their begin/end.
 		</constant>