Release MERFISH imputed gene data.

[morriscb]

• [x] Add merfish imputed jupyter notebook example and update relevant links.
• [x] Add merfish imputed description md and related links.
• [x] Create gene resource page for imputed data. https://alleninstitute.github.io/abc_atlas_access/docs/gene_lists/README.html
• [x] Create automated code to create manifest from directory.
• [x] Upload new imputed h5ad file and metadata.
• [x] Finalize notebooks with science team
• [x] Finalize manifest and upload.
• [x] Test download of all data with new manifest
• [x] Run all notebooks with new manifest.
• [x] Remove extra code to hack in manifest.