add: extrude option.

[MioMioReimu]

Extrude repeats the sprite's pixels at the border. Sprite's size is not changed.

There are two uses for this:

• Reduce flickering in some cases where sprites have to be put next to each other in the final program.
• Check if sprite outlines are OK. E.g. if you want to use sprites to create tilemaps this allows you to see if there are semi-transparent pixels at the borders of the tiles.

It work just same as in TexturePackerGUI.

[wo1fsea]

add: extrude option.