Add SlotVFX to Animation (#491)

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

README.md

@@ -158,6 +158,7 @@ _Great graphics placeholders and tools to turn that squared game into a picasso
 - :tada: [NixieFX](https://nixiefx.com/) - Free browser-based particle and VFX editor for Three.js and PixiJS web games, with an open-source runtime.
 - :tada: [Pixel Composer](https://github.com/Ttanasart-pt/Pixel-Composer) - Powerful node-based VFX editor for pixel art
 - :moneybag: [Riggy](https://riggyapp.com/) - AI rigs a layered PSD into a Spine 4.2 skeleton with animations from a text description; exports plain skeleton.json and atlas.
+- :money_with_wings: [SlotVFX](https://slotvfx.com/) - Desktop editor for particles and game VFX with Spine support. Free to use; exports for Pixi, Phaser, Cocos Creator and WebGL2 need a paid plan.
 - :moneybag: [Spine](https://esotericsoftware.com/) - Spine is dedicated to 2D animation, providing an efficient workflow both for creating amazing animation and for integrating it into your games.
 - :moneybag: [Spriter Pro](https://brashmonkey.com/download-spriter-pro/) - Modern tool for sprite animation.