Add updated release timeline doodle

[jlenh]

Description

Adds the wonderful release timeline doodle from here to the release documentation.

Closes #2895

Link to documentation: https://esmvaltool--2899.org.readthedocs.build/projects/ESMValCore/en/2899/

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.63%. Comparing base (8de26a5) to head (6b0667d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2899   +/-   ##
=======================================
  Coverage   95.63%   95.63%           
=======================================
  Files         263      263           
  Lines       15492    15492           
=======================================
  Hits        14816    14816           
  Misses        676      676           

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[jlenh]

We should think about re-formatting the doodle later on as it is not really readable as such in the narrow documentation page @ehogan

[bouweandela]

Maybe you could add a bit of code so you can click it to enlarge?

[jlenh]

Maybe you could add a bit of code so you can click it to enlarge?

Done in 6b0667d

[bouweandela]

Thanks! Unfortunately it doesn't work for me, when I click the image I see

[valeriupredoi]

the problem is that the image is rendered from figures which is not a source for RTD, it needs be rendered from build/_images - try the same syntax as in index.rst - that picture, albeit small, it renders from the correct build location:

.. container::
   :name: figarch

   .. figure:: figures/ESMValSchemaDiagram.png
      :alt: Brief topics for tool and core.
      :class: dark-light