warn many shapes as points

[melonora]

closes #213

This PR checks whether there is a point geometry in a shapes element and if the length of the element exceeds 1m adds an icon to the list widget item. When a user then hovers over the item they get to see a warning regarding visualization.

[melonora]

This could also potentially be extended to put warning signs and tooltips for the subsampling of points.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 86.66667% with 2 lines in your changes are missing coverage. Please review.

❗ No coverage uploaded for pull request base (main@83ef3d8). Click here to learn what that means.

Files	Patch %	Lines
src/napari_spatialdata/_sdata_widgets.py	86.66%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #224   +/-   ##
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  Coverage        ?   75.88%           
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  Files           ?       18           
  Lines           ?     2015           
  Branches        ?        0           
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  Hits            ?     1529           
  Misses          ?      486           
  Partials        ?        0           

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[LucaMarconato]

Thanks, this looks great! As discussed I have reduced the threshold, extended this to polygons/multipolygons (with a lower threshold) and moved the constants to the config.py file.