Add documentation infrastructure

Add documentation infrastructure and some sample content.

Documentation is generated by sphinx using extensions to support
Markdown an restructuredText for simple documentation writing.

Signed-off-by: Bobby Noelte <b0661n0e17e@gmail.com>

docs/develop/CONTRIBUTING.md

@@ -0,0 +1,48 @@
+# Contributing to EOS
+
+Thanks for taking the time to read this!
+
+The `EOS` project is in early development, therefore we encourage contribution in the following ways:
+
+## Bug Reports
+
+Please report flaws or vulnerabilities in the [GitHub Issue Tracker]((https://github.com/Akkudoktor-EOS/EOS/issues)) using the corresponding issue template.
+
+## Ideas & Features
+
+Please first discuss the idea in a [GitHub Discussion](https://github.com/Akkudoktor-EOS/EOS/discussions) or the [Akkudoktor Forum](https://www.akkudoktor.net/forum/diy-energie-optimierungssystem-opensource-projekt/) before opening an issue.
+
+There are just too many possibilities and the project would drown in tickets otherwise.
+
+## Code Contributions
+
+We welcome code contributions and bug fixes via [Pull Requests](https://github.com/Akkudoktor-EOS/EOS/pulls).
+To make collaboration easier, we require pull requests to pass code style and unit tests.
+
+### Code Style
+
+Our code style checks use [`pre-commit`](https://pre-commit.com).
+
+```bash
+pip install -r requirements.txt
+```
+
+To run formatting automatically before every commit:
+
+```bash
+pre-commit install
+```
+
+Or run them manually:
+
+```bash
+pre-commit --all
+```
+
+### Tests
+
+Use `pytest` to run tests locally:
+
+```bash
+python -m pytest -vs --cov modules --cov-report term-missing tests/
+```