pre-commit hooks for docstrings documentation and MkDocs build

.pre-commit-config_docs.yaml

    - id: automate_functions
      name: Add functions to mkgendocs configurations YAML
      entry: bash -c "python3 Python\ tips/automate.py; git add -u" --
      language: system
    - id: mkgendocs
      name: Generate markdown from docstrings
      entry: bash -c "gendocs --config 'mkgendocs.yml'; git add -u" --
      language: system
    - id: mkbuild
      name: Build the markdown documentation, run with '$ mkdocs serve' at http://127.0.0.1:8000/
      entry: bash -c 'mkdocs build'
      language: system