Canvas Rotation

There's already tile rotation in the game, but there isn't any ability to rotate the entire canvas, which is helpful when working on individual large images (especially with tablets, where some types of strokes are easier than others). I found myself having to do so with a recent project. Since we switched from a landscape to a portrait resolution (switched from a side-scrolling shmup to a vertical/top-down one), I had to save my background piece to png, open it in another image editor, rotate it, and import back into PyxelEdit- not necessarily workflow friendly.