Styling and dev tools

[hannah-macdonald1]

• Adds prettier & eslint with husky pre-commit hook. Note that you may need to run "npm run prepare" to set up the hook correctly
• Adds jest, supertest & jest-fetch-mock for testing, as well a sample test (use "npm run test")
• Adds nodemon for easy rerunning on save of changes (use "npm run dev")
• Update license information

Finishes part of https://deloittedigital.atlassian.net/jira/software/projects/BVPS/boards/535?selectedIssue=BVPS-54