Use automated tests

[henriquecbuss]

What we have
Right now we test everything manually, which makes it easy to let some edge cases slip in to the final build. Our development process goes like this right now:

1. Produce code
2. Test locally
3. Fix code if needed
4. Get a review from a teammate, and fix the code if needed. Repeat this until the PR is approved
5. Ask one of the designers to test the PR. If they request changes, go back to 4.
6. Once a dev and a designer have approved the PR, be happy and merge it.

Proposal
We should start using automated tests

Why
This would improve the overall quality of our app, and ensure we don't break anything between updates. We also would require less time from the design team to test things, which means they gain time and we gain time, win-win!

How
Probably using elm-test initially. In the future, we could look into tools like Selenium to do some more advanced tests.

Additional context
N/A