Many updates to documentation, add docstyle linting

[tlambert03]

This PR makes a lot of updates to the documentation,

• uses sphinx.ext.napoleon to properly parse docstrings
• applies linting to documentation using pydocstyle, enforcing style consistency (including PEP257 style enforcing that the first line of the docstring fits on a single line)
• adds intersphinx links to external docs/classes
• adds sphinx_autodoc_typehints to docs deps and removes duplicated type info from docstrings Args sections (that plugin can pull them directly from the signatures)

example parameters section before this PR:

example after this PR:

[codecov-commenter]

Codecov Report

Merging #46 (108c79e) into main (8830ca6) will decrease coverage by 0.22%.
The diff coverage is 81.81%.

@@            Coverage Diff             @@
##             main      #46      +/-   ##
==========================================
- Coverage   92.86%   92.65%   -0.22%     
==========================================
  Files          32       32              
  Lines         757      762       +5     
==========================================
+ Hits          703      706       +3     
- Misses         54       56       +2     

Files	Coverage Δ
motile/constraints/constraint.py	100.00% <ø> (ø)
motile/constraints/expression.py	92.50% <ø> (ø)
motile/constraints/max_children.py	100.00% <ø> (ø)
motile/constraints/max_parents.py	100.00% <ø> (ø)
motile/constraints/pin.py	100.00% <ø> (ø)
motile/constraints/select_edge_nodes.py	100.00% <ø> (ø)
motile/costs/appear.py	100.00% <ø> (ø)
motile/costs/costs.py	85.71% <ø> (ø)
motile/costs/disappear.py	100.00% <ø> (ø)
motile/costs/edge_distance.py	47.05% <ø> (ø)
... and 17 more