pyodide compatibility

[simontaurus]

e.g. to use https://pawamoy.github.io/markdown-exec/usage/pyodide/#exec-60--rendered (currently pyodide 0.23.0)

Can't find a pure Python 3 wheel for: 'mwparserfromhell', 'pybars3', 'pyyaml>=6.0.1' See: https://pyodide.org/en/stable/usage/faq.html#micropip-can-t-find-a-pure-python-wheel

• https://github.com/wbond/pybars3 Mandatory, pure python => wheel build needed
• https://github.com/earwig/mwparserfromhell Optional, has C-components => move to optional dep.
• https://github.com/yaml/pyyaml: Already supported in latest pyodide