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).

git-subtree-dir: db-update-mockup
git-subtree-mainline: cdb482b3
git-subtree-split: 1487bcc3

README.rst: Adding examples for per-package plaintext files based tracking of versions and per-repo plaintext files based tracking of package versions (both don't hold any further packge information but name and version).