fix: specify ass_set_storage_size

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

Cherry-picked from: ThaUnknown/jassub@0c258cf

References:
[1] libass/libass#591

src/SubtitleOctopus.cpp

@@ -375,6 +375,7 @@ class SubtitleOctopus {
     /* 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;
     }