multi-package demo notebook

[EddyCMWF]

Description

An additional notebook for the Tutorials that combines ek-data, -geo, -meteo, -transforms and -plots. Was one I had in a branch of the training event repo, and seemed a shame to lose it.

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• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

[Oisin-M]

@EddyCMWF this looks great, but one small request - can you change the title away from "Multi Earthkit package workflow"? All of the examples in the earthkit toplevel docs should be using multiple packages. I would call it some description of what the workflow does e.g. UK Regions Analysis or something

[EddyCMWF]

Thanks @Oisin-M ,
I addressed your comments, part of which meant I changed the final plot to be of relative humidity instead of temperature to make it a more focussed on humidity so that the title can be more specific.
Eddy