Add integration tests for key workflows like "create project"

[jamiew]

We just had a javascript quirk in the "create project" form block people from creating projects: https://github.com/helpwithcovid/covid-volunteers/pull/163

It would be awesome to add end-to-end, javascript-and-all system tests for that page, varying the input fields to confirm validations work and edge-cases like this don't regress.