When designing for GitHub CLI, there are several ways you can go about prototyping your ideas.
Google Docs

Best for simple quick illustrations of most ideas
Use this template, or format your document with these steps:
- Choose a dark background (File > Page Setup > Page Color)
- Choose a light text color
- Choose a monospace font
Tips
- Mix it up since people’s setups change so much. Not everyone uses dark background!
- Make use of the document outline and headers to help communicate your ideas
Figma

If you need to show a process unfolding over time, or need to show a prototype that feels more real to users, Figma or code prototypes are best.
Figma library (accessible to GitHub staff only)