Added Voidsprite

Please confirm this pull request meets the following requirements:

• [ X ] I followed the contributing guidelines: https://github.com/github/explore/blob/main/CONTRIBUTING.md.
• [ X ] This change is not self-promotion.

Which change are you proposing?

• [ X ] Suggesting edits to an existing topic or collection
• Curating a new topic or collection
• Something that does not neatly fit into the binary options above

Editing an existing topic or collection

I'm suggesting these edits to an existing topic or collection:

• Image (and my file is *.png, square, dimensions 288x288, size <= 75 kB)
• [ X ] Content (and my changes are in index.md)

Voidsprite is a FOSS pixelart editor with broad format support, split session canvases, isometric texture preview, RPGMaker map preview and many other general convenience and QOL features.