Add example of schema validation test with Joi

[stefanteixeira]

Description

Adding a simple schema validation test with Joi, to demonstrate how it can be done. Also, removing expect-playwright lib, which was unnecessary (closes #42)

How to test

• yarn install
• yarn api:start
• yarn test:api

Checklist

• Branch name follows the pattern: concise-feature-description
• PR has a descriptive name
• PR branch is up-to-date with main (if not, rebase it)
• Double-check the quality of commit messages

[uLucasFraga]

@stefanteixeira Would you find it interesting to have a folder just for schemas?

For example:

• api/schemas
• e2e

or:

• api
• schemas
• e2e
• visual

Because I think it would be easier to increase testing and your maintenance (if necessary).
Ah...and to separate a job for schema test.

[stefanteixeira]

@uLucasFraga I wouldn't split this schema validation from API tests because they rely on the same structure and are an API test anyways.

Regarding having a separate place for schemas, it's definitely worth it 👍
I'll move it to lib/schemas.js for now and import in the API test added in the PR, WDYT?

[uLucasFraga]

LGTM! 🐐