Allow Users to Override stdin when loading Pyodide

[JeffersGlass]

Checklist

• I added a descriptive title
• I searched for other feature requests and couldn't find a duplicate (including also the type-feature tag)
• I confirmed that it's not related to another project are area (see the above section)

What is the idea?

Since version 0.18.0, Pyodide allows the user to override the default requests from stdin. I propose adding an option to allow the user to define a different typescript/javascript function to use for stdin, perhaps awaiting input from a given <input>?

Why is this needed

The current behavior of using input() within a py-script tag is to create a browser prompt with the given text. This is a good default, but perhaps not ideal in all situations, and doesn't "feel" how input() does work working, say, in a REPL.

What should happen?

The user should be able to (somehow) specify a Javascript function, defined before the Pyodide runtime loads, to use for stdin.

Additional Context

Presumably this is a relatively straightforward modification to loadInterpreter(), but as to where the user would actually configure such an option I'm not sure.

Or perhaps it's as simple as defining a javascript function with a specific name, then, if that function is available in the js global scope importing that via from js import... and using that in the loadPyodide() call?