You can find it hosted here: https://playground.extism.org/
The Extism Playground allows you to run and experiment with Extism Plugins in the browser using the Extism browser runtime. It gives you a nice interface for loading plugins from the web or your disk and for sending test inputs and rendering different outputs.
This project was bootstrapped with Create React App. You can learn more in the Create React App documentation. To learn React, check out the React documentation.