Set up a continuous integration pipeline

As a developer I want to use continuous integration to reliably build, test and deploy my project but I don't want to manually set it up everytime.

Acceptance criteria

[ ] It should use CircleCI
[ ] It should run the rspec test suite on pull requests
[ ] It should run the frontend jest test suite on pull requests
[ ] It should build the project e.g. bundle install & yarn install
[ ] It should run db migrations
[ ] It should run linting tools
[ ] It should run security audits on dependencies and the code
[ ] If it passes on a pull request, it should deploy a review app
[ ] On a merge / rebase into main it should re-run the ci pipeline and if successful deploy to staging
[ ] Deployment to production should only ever be done manually after evaluating staging