Log Message:
py-cairo: update to 1.20.0.

1.20.0 - 2020-10-05
-------------------

* Require Python 3.6+ :pr:`201`
* Require cairo 1.15.10+ :pr:`204`
* docs: support Sphinx 3.0 :pr:`207`
* meson: add 'tests' option to skip tests :pr:`188`
* Windows: build wheels :pr:`197`
* Add support for Python 3.9 and 3.10 :pr:`198` :pr:`202`
* examples: add a Jupyter Notebook example :pr:`181`
* Raise an error early when being passed a file object not opened in binary mode \ 
:pr:`205`
* Add a pyproject.toml file :pr:`206`