Add dropdowns to all chapter for `key takeaways` and `environment setup` #773

Job	Run time
Build-environments (jupyter-book/introduction/analysis_tools.yml)	35s
Build-environments (jupyter-book/preprocessing_visualization/preprocessing.yml)	1m 5s
Build-environments (jupyter-book/cellular_structure/clustering.yml)	42s
Build-environments (jupyter-book/cellular_structure/annotation.yml)	2m 55s
Build-environments (jupyter-book/cellular_structure/integration.yml)	1m 17s
Build-environments (jupyter-book/conditions/compositional.yml)	2m 39s
Build-environments (jupyter-book/conditions/gsea_pathway.yml)	59s
Build-environments (jupyter-book/conditions/perturbation_modeling.yml)	2m 39s
Build-environments (jupyter-book/conditions/differential_gene_expression.yml)	2m 47s
Build-environments (jupyter-book/trajectories/lineage_tracing.yml)	1m 51s
Build-environments (jupyter-book/trajectories/pseudotemporal.yml)	36s
Build-environments (jupyter-book/mechanisms/cell_cell_communication.yml)	1m 17s
Build-environments (jupyter-book/spatial/spatial.yml)	15m 26s
Build-environments (jupyter-book/surface_protein/surface_protein.yml)	35s
Build-environments (jupyter-book/multimodal_integration/paired_integration.yml)	2m 39s
Build-environments (jupyter-book/multimodal_integration/advanced_integration.yml)	2m 52s
	40m 54s

Provide feedback