Porting causal identification notebook to MMM multidimensional

[cetagostini]

Description

The following should solve the issue #2185 and port the causal identification notebook.

Related Issue

• Closes Port Introduction to Understanding Causal Relationships in Media Mix Modeling to MMM Multidimensional API #2185
• Related to #

Checklist

• Checked that the pre-commit linting/style checks pass. Feel free to comment pre-commit.ci autofix to auto-fix.
• Included tests that prove the fix is effective or that the new feature works
• Added necessary documentation (docstrings and/or example notebooks) using numpydoc format.
• If you are a pro: each commit corresponds to a relevant logical change

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📚 Documentation preview 📚: https://pymc-marketing--2189.org.readthedocs.build/en/2189/

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[cetagostini]

I need to crack a better HSGP than the default, just as we did in the original notebook. Parameters for the new HSGP are different, so it took more than expected, I'll continue during this week.

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