Update build-publish-docs.yml

Adds `nbsphinx` lib to workflow dependencies

.github/workflows/build-publish-docs.yml

@@ -30,6 +30,7 @@ jobs:
         shell: bash -l {0}
         run: |
           python -m pip install --user -e .[docs]
+          python -m pip install nbsphinx
       - name: Builds the documentation
         shell: bash -l {0}
         run: |