Pyodide support

[simontaurus]

Pyodide is a python distribution for the browser and Node.js based on WebAssembly. Especially useful for playgrounds/education (e. g. JupyterLite) and interactive documentation (e. g. markdown-exec)

Pure python packages are directly supported, but packages with C extensions like mwparserfromhell need to be handled explicitly.

@earwig Would you be interested in providing a pyodide package?
It shouldn't be much efford, since https://github.com/conda-forge/mwparserfromhell-feedstock/blob/main/recipe/meta.yaml is already in place