ENH: add neighbors

[martinfleis]

Easy one this time. Hard to time, as cardinalities are cached.

# first run (weighted)
    # CPU times: user 49.5 ms, sys: 121 ms, total: 170 ms
    # Wall time: 179 ms
# timeit
    # 25.7 ms ± 190 µs per loop (mean ± std. dev. of 7 runs, 10 loops each) - new
    # 549 ms ± 2.07 ms per loop (mean ± std. dev. of 7 runs, 1 loop each) - old

Faster esp. if other function before called cardinalities.

[martinfleis]

This is to avoid converting

    if weighted:
        r = graph.cardinalities / geometry.length
    else:
        r = graph.cardinalities

into an inline. I find this way more readable.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.6%. Comparing base (4037c70) to head (46310e8).
Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #557     +/-   ##
=======================================
+ Coverage   97.4%   97.6%   +0.3%     
=======================================
  Files         26      30      +4     
  Lines       4328    4818    +490     
=======================================
+ Hits        4214    4704    +490     
  Misses       114     114             

Files	Coverage Δ
momepy/functional/_distribution.py	100.0% <100.0%> (ø)
momepy/functional/tests/test_distribution.py	100.0% <100.0%> (ø)