Add link to live version of the explorer with an upload area

[MarcSkovMadsen]

To give users something useful right away it would be quite powerful to provide a link to a live version (powered by pyodide) of the Explorer composed with a FileUpload and a CodeArea to copy paste.

Try it out here

[jbednar]

Definitely! I think a live example would be really useful even without the upload or paste support, just so that people can get an interactive experience of working with these tools.