Create challenges with I/O

create challenges where one needs to read (and maybe even write) to csv/excel, etc.

We need write these files in the pyodide filesystem and run the tests against this. Note that the `transform` function might not be the best choice for this. Maybe we need to generalize this

Start by tracing the existing transform function and how challenges are executed in the Pyodide filesystem. Check how current tests invoke challenges; done means a challenge can read and optionally write CSV or Excel files in that filesystem and tests run against those files.

Written by the indexing model from the issue text.