Add CI for testing on PRs

[tmyracle]

Addresses #178

Tested on my forked repo: https://github.com/tmyracle/maybe/actions/runs/7621318372

Steps that still need to be done:

• Create an Environment in the Maybe repo settings called "Testing"
• Add the secrets that are being called from secrets in the yaml file (make sure the Polygon tier is set to "starter" so that the tests don't timeout, API key shouldn't matter since requests are mocked with nock)
• Add branch protection rule to main to require the workflow to succeed before merging

The run on this PR will fail until the secrets are added, but should succeed after that.