add centroid return value to beamenergy

[BrianGun]

Pull Request Template

Description

added centroid return value to beamenergy function.

Fixes #321

Type of change

• Bug fix (non-breaking change which fixes an issue)
• [ x] New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

passed unit tests

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[codecov-commenter]

Codecov Report

Merging #322 (e5ef743) into main (1661d8b) will increase coverage by 0.01%.
The diff coverage is 62.22%.

@@            Coverage Diff             @@
##             main     #322      +/-   ##
==========================================
+ Coverage   54.56%   54.58%   +0.01%     
==========================================
  Files          78       78              
  Lines        7079     7081       +2     
==========================================
+ Hits         3863     3865       +2     
  Misses       3216     3216              

Impacted Files	Coverage Δ
src/Optical/ParaxialAnalysis/LensletAssembly.jl	60.97% <62.22%> (+0.97%)	⬆️

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