Pyxdg

* BaseDirectory: Add support for $XDG_STATE_DIR

* Fix some ResourceWarnings
* Fix compatibility with Python >= 3.8.4
* Fix some bugs in xdg.Menu

* DesktopEntry: Add a method to check the existence of the TryExec value,
Debian bug 618514.

* Add support for $XDG_RUNTIME_DIR, Debian bug 656338.
* Allow desktop entry files that are not encoded in UTF-8, Debian bug 693855.
* Mime: Add support for subclasses and aliases.

* Update allowed DesktopEntry categories following changes to the
specification.
* Fix removal of empty submenu, freedesktop bug 54747.
* Documentation is now available on RTD: http://pyxdg.readthedocs.org/
* A few more tests, and some code cleanup.
* Fix failure to parse some menu files when kde-config is missing,
freedesktop bug 56426.

* Fix a test for non-UTF-8 locales.