docs(AstrodynamicalCalculations): add usage examples

[cadojo]

Changes

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Reviewer: @cadojo

[codecov]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.43%. Comparing base (8cd29ca) to head (287c0d7).

Files with missing lines	Patch %	Lines
...AstrodynamicalCalculations/src/R2BPCalculations.jl	0.00%	3 Missing ⚠️

❌ Your patch check has failed because the patch coverage (0.00%) is below the target coverage (90.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #265      +/-   ##
==========================================
+ Coverage   54.14%   56.43%   +2.28%     
==========================================
  Files          13       13              
  Lines        1206     1212       +6     
==========================================
+ Hits          653      684      +31     
+ Misses        553      528      -25     

Flag	Coverage Δ
AstrodynamicalCalculations.jl	51.09% <0.00%> (+3.61%)	⬆️
AstrodynamicalModels.jl	67.97% <ø> (ø)
AstrodynamicalSolvers.jl	64.62% <ø> (ø)
GeneralAstrodynamics.jl	0.00% <ø> (ø)

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