Introduce mypy, pylint, isort, gitlab-ci pre-commit hooks

Pre-commit hooks

`mypy`

Introduce mypy pre-commit hook

`pylint`

Introduce pylint pre-commit hook
- #135 (closed): Move pylint conf to pyproject.toml

`isort`

Introduce pre-commit hook
Sort imports
Introduce isort job
- Install isort on the 3.8 image

`gitlab-ci`

Doing requests on a GitLab instance

Update documentation

Edited May 13, 2021 by Moul

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