ci: Add Github actions

[isidroamv]

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[isidroamv]

@Divide-By-0 Please add the variable ALCHEMY_API_KEY in the project config and re-run the test. In addition, configure the project to block merges if the tests don't pass.

[isidroamv]

@Divide-By-0 Could you please configure the environment variable as the image below?

[Divide-By-0]

@isidroamv great! I will merge. We can greatly improve these tests, I added it to #9. For starters, we shuold rename the circuit tests to contract tests since that what they currently are!

unit tests only have this right now:

PASS tests/e2e-ui.test.ts (11.786 s)
  App.js
    ✓ should allow email and eth addr to be entered into inputs (1217 ms)
    ✓ should start with an enabled prove button and status should be 'not-started' (1217 ms)

These only test trivial UI functionality; they don't actually verify the download functionality or witness generation works -- can we add tests for those?