proofwidgets dependency

Does SciLean depend on proofWidgets? I see the reference in the [lake-manifest.json](https://github.com/lecopivo/SciLean/blob/master/lake-manifest.json), but I didn't see the reference in the [lakefile.lean](https://github.com/lecopivo/SciLean/blob/master/lakefile.lean). Can you confirm? In particular, I am working in a project that depends on both, and we may need to eventually also contribute to proofWidgets (see https://github.com/leanprover-community/ProofWidgets4/issues/110).