Add pre-commit configuration file

[mdeweerd]

This adds a pre-commit configuration file.

Enable by:

1. installing pre-commit (pip install pre-commit).
2. Runpre-commit install inside the clone (to run on each commit).

Run on all files with: pre-commit run -a.

Example to run only specific step;:

• `pre-commit run shellcheck -a"

For shellcheck I've ignore several warnings to limit to only a few that if disable could hide important issues.