feature(subtitles): add frog_subtitles addon

addons/frog_subtitles/nodes/VideoStreamSubtitles.cs

@@ -0,0 +1,16 @@
+using Godot;
+
+namespace Frog;
+
+public partial class VideoStreamSubtitles : StreamSubtitles
+{
+    [Export] private VideoStreamPlayer? player;
+
+    public override void _Process(double delta)
+    {
+        if (this.player.Visible && this.player.IsPlaying())
+        {
+            this.UpdateContent(this.player.StreamPosition);
+        }
+    }
+}