Add simple dev instructions

README.md

@@ -2,7 +2,13 @@
 
 # mailcow: dockerized documentation
 
-
 This project aims to provide the mailcow: dockerized documention for the [mailcow: dockerized](https://github.com/mailcow/mailcow-dockerized) project.
 
 https://mailcow.github.io/mailcow-dockerized-docs
+
+To build it locally, you need the [Material theme for MkDocs](https://squidfunk.github.io/mkdocs-material/), [MkDocs](https://www.mkdocs.org/) itself and [Pygments](http://pygments.org/). To install these with [pip](https://pip.pypa.io/en/stable/) and get it up and running, fire up your terminal and enter
+
+```
+pip install mkdocs-material
+mkdocs serve
+```