ENH: return same object as is given in close_gaps and extend_lines

[martinfleis]

Resolves pysal/momepy#723

Technically a breaking change but here we are at 0.1 and in momepy we are deprecating it, so I'd say it is fine?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.8%. Comparing base (b7421ac) to head (5b58a57).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #286     +/-   ##
=======================================
- Coverage   99.1%   98.8%   -0.2%     
=======================================
  Files          7       7             
  Lines       1274    1282      +8     
=======================================
+ Hits        1262    1267      +5     
- Misses        12      15      +3     

Files with missing lines	Coverage Δ
neatnet/gaps.py	100.0% <100.0%> (ø)

... and 1 file with indirect coverage changes

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[jGaboardi]

so I'd say it is fine?

Agreed, it's fine.