fix: specify ass_set_storage_size

According to [1], `ass_set_storage_size` must be called to render transforms correctly.

References:
[1] https://github.com/libass/libass/issues/591

Cherry-picked from: 0c258cf996

src/SubtitleOctopus.cpp

@@ -375,6 +375,7 @@ public:
     /* CANVAS */
     void resizeCanvas(int frame_w, int frame_h) {
         ass_set_frame_size(ass_renderer, frame_w, frame_h);
+        ass_set_storage_size(ass_renderer, frame_w, frame_h);
         canvas_h = frame_h;
         canvas_w = frame_w;
     }