Updates to ParmEst documentation

[slilonfe5]

Summary/Motivation:

The current documentation of ParmEst does not provide a detailed and step-by-step guide on using ParmEst to perform model-building tasks such as parameter estimation and covariance matrix calculation.

Changes proposed in this PR:

• Add a step-by-step guide on how to create the Experiment class and its list using the simple Rooney-Biegler paper example
• Link the parameter estimation page to the covariance matrix estimation page to refer users to creating the Experiment class and its list.

Legal Acknowledgement

By contributing to this software project, I have read the contribution guide and agree to the following terms and conditions for my contribution:

1. I agree my contributions are submitted under the BSD license.
2. I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.40%. Comparing base (13facca) to head (104a635).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3791      +/-   ##
==========================================
- Coverage   89.40%   89.40%   -0.01%     
==========================================
  Files         909      909              
  Lines      105541   105541              
==========================================
- Hits        94364    94355       -9     
- Misses      11177    11186       +9     

Flag	Coverage Δ
builders	29.10% <ø> (-0.01%)	⬇️
default	86.02% <ø> (?)
expensive	35.76% <ø> (?)
linux	86.71% <ø> (-2.47%)	⬇️
linux_other	86.71% <ø> (-0.01%)	⬇️
osx	82.86% <ø> (-0.01%)	⬇️
win	84.96% <ø> (-0.01%)	⬇️
win_other	84.96% <ø> (-0.01%)	⬇️

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