BUG: sphinx proof is generating warnings

[mmcky]

Describe the bug

context

I have started to get warnings generated by sphinx-proof

WARNING: Domain 'sphinx_proof.domain::prf' has not implemented a `resolve_any_xref` method [myst.domains]

expectation

No warnings produced

Reproduce the bug

Run a build of jupyter-book that uses sphinx-proof is generating warnings across the board.

List your environment

Jupyter Book : 0.15.1 External ToC : 0.3.1 MyST-Parser : 0.18.1 MyST-NB : 0.17.2 Sphinx Book Theme : 1.0.1 Jupyter-Cache : 0.6.1 NbClient : 0.5.13