Import netifaces only if used

[pnuu]

This PR moves the netifaces import inside the trollmoves.utils.get_local_ips() function. This way pip install --no-dependencies trollmoves can be used with minimal additional packages when get_local_ips() isn't needed.

There were also some docstrings missing, which are added here.

• Closes #xxxx
• Tests added
• Fully documented
• Add your name to AUTHORS.md if not there already

[codecov]

Codecov Report

Merging #134 (1425427) into main (dd468fc) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #134      +/-   ##
==========================================
+ Coverage   87.45%   87.47%   +0.01%     
==========================================
  Files          18       18              
  Lines        3979     3983       +4     
==========================================
+ Hits         3480     3484       +4     
  Misses        499      499              

Flag	Coverage Δ
unittests	87.47% <100.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
trollmoves/utils.py	78.82% <100.00%> (+0.25%)	⬆️
trollmoves/server.py	66.14% <0.00%> (-0.11%)	⬇️
trollmoves/client.py	83.40% <0.00%> (+0.18%)	⬆️

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[mraspaud]

LGTM!