Handle bleach deprecation

[MarcSkovMadsen]

Bleach has been deprecated mozilla/bleach#698

nh3 is mentioned as the replacement. It states its 20 times faster. See https://pypi.org/project/nh3/

Checklist

• Replacement must work with pyodide

[MarcSkovMadsen]

nh3 seems not to be installable in pyodide currently.

[philippjfr]

Thanks for filing, we are aware but since security fixes are still backported in bleach and nh3 is a significantly more complex dependency it hasn't been a big priority.