FLASH PR: Sphinx Code Snippets Copy Extension

[JackEAllen]

Add Sphinx-copybutton extension to allow for easy copying of code snippets

Issue

Flash PR

Description

Currently we, don't have a code snippet copy button. This PR adds the extension: sphinx-copybutton to the project to add such a button (see screenshot below)

• Add sphinx-copybutton dependency to environment-dev
• Add sphinx-copybutton to list of sphinx extensions within conf.py

Testing

Describe the tests that were used to verify your changes.

• Rebuild docs and check that code snippets not have a copy button on mouse hover

Rebuild docs: rm -rf docs/build; make build-docs
Run docs: python -m http.server from/mantidimaging/docs/build/html

Acceptance Criteria

How should the reviewer test your changes?

• Code snippets now have a copy code button on mouse hover

Documentation

N/A

[coveralls]

coverage: 72.796%. remained the same
when pulling 76d4a87 on sphinx_code_copy
into aa73fc2 on main.

[samtygier-stfc]

That's handy :-)