⬆️ Update to aiida-core v1.4.0

[chrisjsewell]

✨ Update for compatibility with aiida-core v1.4.0

• ‼️ Drop python 2 support (remove six)
• ‼️ Remove GULP code (moved to aiidaplugins/aiida-gulp package)
• ♻️ Drop local version of BaseRestartWorkChain, and use aiida-core's one
• 👌 Use custom BasisSetFamily group over outdated type string approach
• 👌 Use exposed_outputs method in properties workchain
• 🔧 replace ruamel.yaml with pyyaml

👌 Support for more input variables:

• Add parsing of CRYSTAL ROTCRY input
• Add validation & writing of DFTD3 input block
• Add writing of CHEMOD input block

✨ New PPAN properties calculation, and related parsers

👌 Allow Symmetrise3DStructure to use the pymatgen CIF parser

📚 Update documentation to use myst-nb

🧪 Move to GH Actions for CI testing, and tox configuration, and improve pre-commit code styling

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (develop@9886935). Click here to learn what that means. The diff coverage is n/a.

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