DOC add sphinx link map to scipy

[MatthewSZhang]

Checklist

• Used a personal fork to propose changes
• A reference to a related issue: DOC add intersphinx_mapping for SciPy #220
• A description of the changes: add sphinx map to scipy, especially for scipy optimisers in narx

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (5081306) to head (5bdd861).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #229   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           10        10           
  Lines          859       859           
=========================================
  Hits           859       859           

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