add style guide

Author: matthias_schaub

docs/source/contributing.md

@@ -1,12 +1,46 @@
 # Contributing
 
-This document is a work progress. It should describe how to contribute (code or issues) to the MapSwipe back-end.
 
-To contribute to the MapSwipe back-end please create dedicated feature branches.
+## Clone from GitHub
+
+```bash
+git clone https://github.com/mapswipe/python-mapswipe-workers.git
+cd python-mapswipe-workers
+git checkout dev
+```
+
+
+## Install MapSwipe Workers
+
+Create a Python virtual environment and activate it. Install MapSwipe Workers using pip:
+
+```bash
+python -m venv venv
+source venv/bin/activate
+pip install --editable .
+```
+
+
+## Feature Branch
+
+To contribute to the MapSwipe back-end please create dedicated feature branches:
 
 ```bash
 git checkout -b featureA
 git commit -am 'add new project type'
 git push -u origin featureA
 git request-pull origin/master featureA
 ```
+
+
+## Style Guide
+
+This project uses [black](https://github.com/psf/black) and [flake8](https://gitlab.com/pycqa/flake8) to achieve a unified style.
+
+Use [pre-commit](https://pre-commit.com/) to run `black` and `flake8` prior to any git commit. `pre-commit`, `black` and `flake8` should already be installed in your virtual environment since they are listed in `requirements.txt`. To setup pre-commit simply run:
+
+```
+pre-commit install
+```
+
+From now on `black` and `flake8` should run automatically whenever `git commit` is executed.