Normalized taylordiagram

[coxipi]

Pull Request Checklist:

• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes #xyz
• Tests for the changes have been added (for bug fixes / features)
  • (If applicable) Documentation has been added / updated (for bug fixes / features)
• CHANGES.rst has been updated (with summary of main changes)
  • Link to issue (:issue:number) and pull request (:pull:number) has been added

What kind of change does this PR introduce?

• Add a bool option normalize and divide ref_std, sim_std by ref_std if True

Does this PR introduce a breaking change?

No

Other information:

I was planning a new plot option in figanos, but I was told we don't want to do any computation in figanos, it would be handy that sdba can manage this by itself.

[Zeitsperre]

@coxipi Will merge this once the checks finish. All that's left is #1580 before the release!