598/maskmasker quick plot

[jpolton]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
  • Some docs updates need to be made in the COAsT-site repo, in a separate PR. See contributing to documentation for details.
• Build (./build.sh) was run locally and no errors reported. NB not sure about this requirement: GitActions test this
• Lint (pylint .) has passed locally and any fixes were made for failures. NB not sure about this requirement: GitActions test this with black

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

MaskMaker() is missing a means to visualise regional masks

Issue URL: #598

What is the new behavior?

• MaskMaker.quick_plot() is a means to visualise regional masks
• Updated definitions of English Channel to not overlap with southern North Sea
• Added mask masker tutorial to notebook

Checklist

• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing (pip install . && pytest unit_testing/unit_test.py -s)
• Extended the README / documentation, if necessary
• Added myself / the copyright holder to the AUTHORS file

Does this introduce a breaking change?

• Yes
• No

Other information

[jpolton]

@anwiseNOCL could you do a review of this? Should be straight forward without surprises
Highlights:

• MaskMaker.quick_plot() is a means to visualise regional masks
• Updated definitions of English Channel to not overlap with southern North Sea
• Added mask masker tutorial to notebook

[anwiseNOCL]

No issues here