Update citations for new paper

Description

Add reference to the new paper to the citations and make sure they are recognised by GitHub.

The new paper should be cited from now on.

[x] I have raised an issue to propose this change (required for new features and bug fixes)

[ ] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)
[x] Documentation (update in the documentation)

[x] I have updated the changelog accordingly (required).
[x] My change requires a change to the documentation.
[ ] I have updated the tests accordingly (required for a bug fix or a new feature).
[x] I have updated the documentation accordingly.
[ ] I have reformatted the code and checked that formatting passes (required).
[ ] I have have fixed all issues found by flake8 (required).
[ ] I have ensured that all pytest tests pass (required).
[ ] I have run pytest on a machine with a CUDA GPU and made sure all tests pass (required).
[x] I have checked that the documentation builds (required).

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