Fix typos and command in CONTRIBUTING.md

[danny-lloyd]

General:

• Have you followed the guidelines in our Contributing document?
• Have all checks, quality assurance steps and tests passed?

Quality checks:

• Have you updates the CHANGELOG.rst file?
• Have you updated the version and author attributes (as appropriate) in the pyproject.toml file?

Community standards:

• Have you followed Semantic Versioning?
• Have you updated the docstrings and / or documentation files to reflect your change?

What is the purpose of this change?

The purpose of this change is to improve the docs for contributors.

What does the change consist of?

This change consists of:

• Command for setting up pre-commit hooks was the wrong way round.
• Also fixed a few typos.