It’s a “.java” file. You can download it and then drag & drop into your sketch:
https://Raw.GitHubUserContent.com/GoToLoop/command/patch-1/src/deadpixel/command/Command.java
Now you can import
it like this:
import deadpixel.command.Command;
You can check out the link I’ve posted from my previous reply in order to figure out how to use it.