include IFU page in docs

docs/index.rst

@@ -61,6 +61,7 @@ Contents
    jwst_measured_opds.ipynb
    jwst_detector_effects.ipynb
    jwst_matching_psfs_to_data.ipynb
+   jwst_ifu_datacubes.ipynb
    jwst_large_psf.ipynb
    jwst_optical_budgets.ipynb
    jwst_psf_subtraction.ipynb