pyproject.toml:
Add pydantic to dependencies, as it will be used to validate
configuration and internal typing.

.gitlab-ci.yml:
Add Gitlab CI integration, that runs tox's linter and coverage targets
in a lint stage.

tests/test_convert.py:
Add initial tests for the convert module by adding a parametrized test
for `_files_data_to_dict()`.

repo_management/defaults.py:
Add the basic defaults module, providing data that translates keywords
found in the 'desc' and 'files' files of a binary repository database to
those used in JSON files, representing the same data.

repo_management/convert.py:
Add the convert module, and introduce the simple private method
(reimplementing a subset of the features from db2json)
`_files_data_to_dict()`, which translates the contents of a `files` file
to a typed dict.

tox.ini:
Add tox integration for testing (linting and coverage) in virtual
environments using poetry.

poetry.lock:
Add lock file with all dependencies currently used to test the project.

pyproject.toml:
Add a pyproject.toml for describing the project, configuring all
currently required dependencies and development dependencies.
The configuration adds entries for the code formatter black, the import
sorting tool isort and for the coverage report generation tool coverage.

.gitignore:
Add a ignore file for git, with many default entries for python projects
related files, that should never end up in version control.

.mypy.ini:
As mypy can not yet be configured through pyproject.toml, add a specific
configuration file for it.

.flake8:
As flake8 can not yet be configured in a pyproject.toml, use a specific
file for it.
Set the maximum complexity to 10 (can even be lower) and add default
exclusions for project unrelated files.

.editorconfig:
Add editorconfig integration, that covers .py, .rst and .yml files.

Signed-off-by: Alad Wenter <alad@archlinux.org>

Using 'black'. No config needed for it (yet).