Qeschema

* set max version of xmlschema to 2.3.1 to avoid issues with newer versions
* updates default schema version with the one used in Quantum ESPRESSO

* Fixes and improvements
* New versions of schemas
* Python 3.11 support

* Add optional extra features for HDF5 and YAML

* Update with latest _qes.xsd_ schema
* Add h5py to package requirements
* Drop support for Python 3.6
* Code cleaning and extend tests

Add missing files to repo and package:
- Add MANIFEST.in to repository
- add `qeschema/schemas/releases/*.xsd` to package