Add Figure 3.12 of IPCC WG1 AR6 Ch3 (based on Santer et al. 2021)

[katjaweigel]

Description

Under construction, draft because several people to contribute.

• Closes #issue_number
• Link to documentation: https://github.com/ESMValGroup/ESMValTool/blob/AR6_santer20jclim/doc/sphinx/source/recipes/recipe_ipccwg1ar6ch3_santer20jclim.rst

https://esmvaltool--3471.org.readthedocs.build/projects/ESMValCore/en/3471/recipes/recipe_ipccwg1ar6ch3_santer20jclim.html

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