Update index.md

[ice-nuclearcrackhead239]

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

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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.

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[jmeridth]

@ice-nuclearcrackhead239 need to add the new item to the bottom of the list, not in the middle.