Sprite:saveCopyAs() inconsistence

When saving a sprite as a .png or .jpg, it creates the output directory if it does not exist already. On the other hand, saving as .gif does not create the output directory, resulting in an error instead.

The function creating the directory for you is very comfortable.

Start by locating the Sprite:saveCopyAs() implementation and compare its handling of .png, .jpg, and .gif output paths. Confirm the expected behavior by reproducing the missing-directory case; done means GIF saves create the output directory consistently with PNG and JPG.

Written by the indexing model from the issue text.