release 0.22rc1 is out

hei everyone

please try and test.

Many changes for details see https://docutils.sourceforge.io/HISTORY.html


reStructuredText:
  - Support `CSS3 units`_. This adds "ch", "rem", "vw", "vh", "vmin",
    "vmax", and "Q" to the `supported length units`__. Note that some
    output formats don't support all units.

  - New option "figname" for the `"figure"`_ directive.

  .. _CSS3 units: https://www.w3.org/TR/css-values-3/#lengths
  __ docs/ref/rst/restructuredtext.html#length-units

Document Tree / Docutils DTD
  - Allow multiple <term> elements in a `\<definition_list_item>`__
    (third-party writers may need adaption).
  - The first element in a <figure> may also be a <reference>
    (with nested "clickable" <image>).

  __ docs/ref/doctree.html#definition-list-item

Configuration changes
  - Make MathML the default math_output_ for the "html5" writer.

  - Change the default input_encoding_ from ``None`` (auto-detect) to
"utf-8".

  - Drop short options ``-i`` and ``-o``.
    Use the long equivalents ``--input-encoding`` and ``--output-encoding``.
    (See `command line interface`_ for the rationale.)

  - Rename configuration setting "output" to "output_path_".

  - The manpage writer now recognizes the sections [writers] and
    [manpage writer] with the new setting `text_references`_.

Output changes
  LaTeX:
     Don't wrap references with custom reference-label_ in a ``\hyperref``
     command. The "hyperref" package generates hyperlinks for labels by
     default, so there is no change in the PDF (except for "ref*").

     Stop requiring "ifthen.sty". Replace use of
     ``\ifthenelse{\isundefined...`` with the eTeX primitive ``\ifdefined``.

  HTML5:
     Unitless image_ size measures__ are written as <img> "width" and
     "hight" values instead of "style" rules.  The current behaviour
     is kept for values with units, so users may specify, e.g. ``:width:
     50px`` instead of ``:width: 50`` to override CSS stylesheet rules.

     __ docs/ref/doctree.html#measure

  manpage:
     Don't UPPERCASE section headings.
     Handle hyperlink references (see text_references_).

  null:
     The "null" writer output changed from None to the empty string.

     `publish_string()` now returns a `bytes` or `str` instance
     for all writers (as documented).

New objects
  `parsers.docutils_xml`
     parser for `Docutils XML`_ (e.g., the output of the "xml" writer).
     Provisional.

     Try ``docutils --parser=xml test/data/multiple-term-definitions.xml``
     or use the :parser: option of the `"include"`_ directive to include
     an XML file in a rST document.

  `nodes.Element.validate()`
     Raise `nodes.ValidationError` if the element does not comply with
     the `Docutils Document Model`_.
     Provisional.

  `writers.DoctreeTranslator`
     Generic Docutils document tree translator base class with
     `uri2path()` auxiliary method.
     Provisional.

Removed objects
  `core.Publisher.setup_option_parser()`
     internal, obsolete,
  `frontend.ConfigParser.get_section()`
     obsoleted by the configparser's "Mapping Protocol Access",
  `frontend.OptionParser.set_defaults_from_dict()`
     obsolete,
  `nodes.Element.set_class()`
     obsolete, append to Element['classes'] directly,
  `parsers.rst.directives.tables.CSVTable.decode_from_csv()`
     not required with Python 3,
  `parsers.rst.directives.tables.CSVTable.encode_from_csv()`
     not required with Python 3,
  `transforms.writer_aux.Compound`
     not used since Dec 2010,
  `utils.error_reporting`
     obsolete in Python 3,
  `utils.Reporter.set_conditions()`
     obsolete, set attributes via configuration settings or directly.

Removed localisations
  Mistranslations of the "admonition" directive name:
     Use "advies" (af), "varsel" (da), "warnhinweis" (de), "aviso" (es),
     "sciigo" (eo), "annonce" (fr), "avviso" (it), "advies" (nl),
     "zauważenie" (pl) (introduced in Docutils 0.21)
     or the English name "admonition".

New files
  ``docutils/parsers/rst/include/html-roles.txt``
     `Standard definition file`_ for additional roles matching HTML tags.

Removed files
  ``tools/rst2odt_prepstyles.py``
     Obsoleted by `writers.odf_odt.prepstyles`.
  ``docutils/utils/roman.py``
     Obsoleted by ``docutils/utils/_roman_numerals.py``

Bugfixes and improvements (see HISTORY_).