Set up CI and NPM package

[lukehesluke]

Like other Node.js OpenActive repos, this repo should be set up to, when there are changes to the master branch:

• Test changes (npm test)
• Increment NPM version
• Publish to NPM
  • an NPM package will need to be made also

Additionally, dependabot and any other GitHub actions that are normally set up for Node.js OpenActive repos.

https://github.com/openactive/data-models might be a good example of this.

[lukehesluke]

This might be easiest to accomplish once the GitHub CI workflows have been centralised as per openactive/github-actions-workflows#2