Develop spatial workshop submodule four

[sjspielman]

This epic tracks work to develop the fourth spatial workshop submodule on neighborhood analyses, potentially at the cell level (e.g. with Visium HD segmentation data).

Goals for this epic include:

• Outline submodule 4 instruction notebook, including the dataset to use
• Complete submodule 4 instruction notebook
• Outline submodule 4 exercise notebook, including the dataset to use
• Complete submodule 4 exercise notebook
• Maintain spatial module cheatsheet