Added function to round the edges of square PSF kernels

[astronomyk]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 75.80%. Comparing base (2d11b6a) to head (1a4b2e9).
Report is 6 commits behind head on main.

Files	Patch %	Lines
scopesim/effects/psfs/semianalytical.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #459      +/-   ##
==========================================
- Coverage   75.80%   75.80%   -0.01%     
==========================================
  Files          64       64              
  Lines        7820     7824       +4     
==========================================
+ Hits         5928     5931       +3     
- Misses       1892     1893       +1     

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