Require `nbconvert`
Require `nbconvert`

Currently we are using `nbconvert` for testing and batch running of the
workflow. While `nbconvert` was an implicit dependency due to `runipy`
being a workflow dependency that needed it, something that is being
directly used in the workflow like `nbconvert` should be explicitly made
a dependency lest `runipy`'s dependencies change (or our dependence on
it). Hence `nbconvert` is added as a dependency of the workflow.

DudLab/nanshe_workflow,nanshe-org/nanshe_workflow