Contribution guide update, configuration page fix.

[kattni]

• Updates the code contribution guide to refer to dependency groups for pip install.
• Updates headings in the configuration reference.

Fixes #2543

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[freakboy3742]

The "." is significant - it's saying "install this directory". It's essentially pip install -e .:

Suggested change

	(.venv) $ python -m pip install -Ue --group dev
	(.venv) $ python -m pip install -Ue . --group dev

[kattni]

Ah ok, I thought it was part of installing using the previous method. Updated.

[freakboy3742]

👍