chore: include supported version of Webots in docs

[abanuelo]

Description

Making explicit mention that Scenic only supports Webots versions >= 2023a.

Issue Link

#260

Checklist

• I have tested the changes locally via pytest and/or other means
• I have added or updated relevant documentation
• I have autoformatted the code with black and isort
• I have added test cases (if applicable)

Additional Notes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.34%. Comparing base (fe28e13) to head (94c7983).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #266      +/-   ##
==========================================
- Coverage   91.42%   91.34%   -0.08%     
==========================================
  Files          54       54              
  Lines       13575    13568       -7     
==========================================
- Hits        12411    12394      -17     
- Misses       1164     1174      +10     

see 6 files with indirect coverage changes