release 0.22rc2

Hei everyone,

only a few changes, but necessary ones to remedy 3rd party problems

please try, test

next release day for 0.22 on my schedule is tuesday june 10.

all the best
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* docutils/parsers/rst/directives/misc.py

  - Pass default settings to custom parser for included file.

* docutils/parsers/rst/states.py

  - Remove the list`states.RSTStateMachine.memo.section_parents`
    (introduced in Docutils 0.22rc1) that broke 3rd-party applications
    setting up a "mock memo".
  - Use `types.SimpleNamespace` instead of a local definition for
    the auxilliary class `states.Struct`.

* docutils/writers/_html_base.py

  - Fix error when determining the document metadata title from the
    source path and the internal `source` attribute is None.