add: Add dev dependencies to user setup.cfg

[joshlynchONS]

Summary

Add an optional dev dependencies section to the users setup file. This helps the user manage the different dependencies between their package users and developers

Checklists

This pull/merge request meets the following requirements:

• code runs
• developments are ethical and secure
• you have made proportionate checks that the code works correctly
• you have tested the build of the template
• test suite passes
• minimum usable documentation written in the docs folder

Comments have been added below around the incomplete checks.

[codecov-commenter]

Codecov Report

Merging #88 (3c48701) into main (1b0652b) will not change coverage.
The diff coverage is n/a.

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@@           Coverage Diff           @@
##             main      #88   +/-   ##
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  Coverage   59.25%   59.25%           
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  Lines          54       54           
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  Hits           32       32           
  Misses         22       22           

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[Jacobb164]

Do we need the pip install here or should it be make install?

Also there is a bit at the bottom of the README.md which say about doing pip install requirements. Can this be replaced / removed and can you check in the other docs it's not there

[joshlynchONS]

Replaced the requirements at the bottom to use the makefile. I've left pip install as an option as well as the Makefile. Do you think I should just keep the Makefile install?