Support pre-commit Framework

[Kurt-von-Laven]

Consider adding a .pre-commit-hooks.yaml to the root of this repository so that Unibeautify may automatically be run locally on each commit. This generally requires no more than 10 lines of YAML. Refer to the pre-commit documentation. Each downstream repository can of course configure its own .pre-commit-config.yaml manually, but doing so essentially requires duplicating the configuration that would go in .pre-commit-hooks.yaml across each downstream project.