Introducing CI with Github Actions

[fao89]

• black style
• github actions

Reference: https://medium.com/@vanflymen/blazing-fast-ci-with-github-actions-poetry-black-and-pytest-9e74299dd4a5

You can check the CI job here: https://github.com/fabricio-aguiar/Flask-GoogleMaps/runs/476086559?check_suite_focus=true