Script updated to v1.2

A nice update to this script.

The Amiga palette mixer dialog window is now modal! You can keep the window open while working on your art.  Furthermore, clicking on the palette swatches in the window (left or right click) will now change the active palette index in Aseprite, and vice-versa.  Your Amiga palette window position will also be remembered if you close and re-open it.

Known bug: the Amiga palette window width/height are unfortunately currently NOT remembered when closing/reopening the window. Will hopefully be included in the next update. (EDIT: This bug was actually due to an Aseprite bug and has been corrected as of Aseprite v1.3)

Thanks to @EntwicklerX for the ideas!

Enjoy!