Online editor

Github on-line editor

Say you have repository at Github
https://github.com/apan-wjc/apan-wjc.github.io
You can easily change the URL from .com to .dev, like this
https://github.dev/github/apan-wjc/apan-wjc.github.io
Then it will redirect you to
https://vscode.dev/github/apan-wjc/apan-wjc.github.io
and open a VSCode like editor window.