docs: update appendix

[Gaiejj]

Description

Move the appendix from our paper to website docs.

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds core functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• I have read the CONTRIBUTION guide. (required)
• My change requires a change to the documentation.
• I have updated the tests accordingly. (required for a bug fix or a new feature)
• I have updated the documentation accordingly.
• I have reformatted the code using make format. (required)
• I have checked the code using make lint. (required)
• I have ensured make test pass. (required)

[codecov]

Codecov Report

Attention: Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.

Project coverage is 96.96%. Comparing base (080e6b8) to head (ef5e25f).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
omnisafe/envs/safety_gymnasium_modelbased.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #350      +/-   ##
==========================================
- Coverage   97.03%   96.96%   -0.08%     
==========================================
  Files         137      136       -1     
  Lines        6906     6768     -138     
==========================================
- Hits         6701     6562     -139     
- Misses        205      206       +1     

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[muchvo]

LGTM.