Migrate to Pyodide 0.29 and jupyterlite 0.7

[FrancescAlted]

Pyodide 0.28 has been recently released, and this is important because it allows maintainers of binary packages (e.g. python-blosc2) to create their own wheels that can be installed, removing the need to include packages in the main pyodide distribution repo. This is a big plus for caterva2, as we don't have to wait (sometimes months) until a new version of python-blosc2 hits the pyodide repo.

More info: https://blog.pyodide.org/posts/0.28-release/

[FrancescAlted]

We should also document how to update pyodide in the future (or it is only jupyterlite that depends on it?).

[jdavid]

Latest version of pyodide now is 0.29
Wait for jupyterlite 0.7 to be released, then upgrade both.