Changes:
* Skip support for Python 3.7
* Update validate geojson (680).
* Sanitize test suite (684, 683, 682, 681).
* Support Python3.10/3.11, documentation fixes, and general codebase cleanup (677).
* Extended env variable interpolation (675)
* Don't use deprecated distutils module (672).
* Fixed tox.ini parameter passenv (670).
* Improve the implementation of pywps.inout.literaltypes (668).
* Fix tests/test_capabilities.py with correct check of request case (665).
* Activate async test (664).
* Move Sleep process definition (663).
* Remove use of mutable as default value in Process.__init__ (660).
* Better handle of crashed processes (659).
* Change coveralls branch from master to main (655).