The readme for @windicss/plugin-animations seems to specify the wrong package:
# @windicss/plugin-animations
Add [Animate CSS](https://github.com/animate-css/animate.css) as [Windi CSS](https://github.com/windicss/windicss) plugin to your project. This plugin is modified based on [tailwind-animate.css](https://github.com/bentzibentz/tailwindcss-animate.css) to adapt to Windi CSS.
## Installation
- npm install --save-dev @windicss/animations
+ npm install --save-dev @windicss/plugin-animations
I think it's also missing types; but maybe that's intentional.