Add PicMason to spritesheet tools (#463)

README.md

@@ -90,6 +90,7 @@ _Great graphics placeholders and tools to turn that squared game into a picasso
 - :tada: [EzSpriteSheet](https://github.com/z64me/EzSpriteSheet) - Creates sprite sheets from animated GIFs and more
 - :tada: [Libgdx Texture Packer](https://github.com/libgdx/libgdx/wiki/Texture-packer) - Texture Packer built into Libgdx
 - :free: [Littera](http://kvazars.com/littera) - Bitmap font generator
+- :free: [PicMason Sprite Sheet Splitter](https://picmason.com/en/sprite-sheet-splitter/) - Browser-based fixed-grid splitter with custom frame sizes, offsets and spacing. Exports PNG frames preserving source transparency and a ZIP with source coordinates; can skip fully transparent frames.
 - :free: [PixelChart Sprite Sheet Tools](https://pixelchart.app/tools/sprite-sheet-maker/) - Pack frames into a sheet with a JSON atlas, slice sheets back into PNGs, and convert between sheets and animated GIFs. Runs in the browser, no upload.
 - :free: [ShoeBox](http://renderhjs.net/shoebox/) - Adobe Air based app with game and ui related tools.
 - :tada: [SnowB Bitmap Font](https://snowb.org/) - Bitmap font generator