Updated readme, changed to pyprojecttoml and added ci

[SamHollings]

• Please check if the Pull Request fulfills these requirements

• The commit message is clear and concise
• Test for the changes have been added and reviewed
• Documentation has been added to all new features and edited code has had documentation reviewed

• What kind of change does this Pull request introduce? (Bug fix, feature, docs update, ...)

  • Stripped the repo down and got the tests working again with the new pyproject.toml, and added CI.

• What is the current behaviour? (Link to a current open issue if possible)

  • The old repo was as it was in Codon, but needed updating, to bring it inline with the standards for the reusable code library

• What is the new behaviour? (is this a feature change?)

  • simpler set of files (just pyproject.toml rather than many config files), and uses github action CI

• Does this Pull Request introduce a breaking change? (What changes might users need to make in their application due to this PR?)

  • yes, but the package hasn't been launched yet.