docs(readme): describe, how to contribute

README.md

 # RDD Technical Reference
+
 Guidelines and references for software development in RDD
 
 To compile in markdown, use
 
-    pandoc --template=rdd.latex rdd-technical-reference.md -o rdd-technical-reference.pdf
+```bash
+pandoc --template=rdd.latex rdd-technical-reference.md -o rdd-technical-reference.pdf
+```
+
+Originally based on the [EURISE Network Technical Reference](https://github.com/eurise-network/technical-reference).
+
+## Contributing
+
+Commits have to be made following a certain convention that is defined by the [Conventional Commit](https://www.conventionalcommits.org/en/v1.0.0/) standard. This repo is designed to be used with [Commitizen](https://github.com/commitizen/cz-cli) for which we provide a configuration in `package.json`.
+
+Install it with
+
+```bash
+npm install
+```
+
+You can now run a commit using commitizen with `git cz`.
 
-Based on https://dariah-eric.github.io/technical-reference/.
+To run commitizen on `git commit` rather than on `git cz`, update or create `.git/hooks/prepare-commit-msg` with the following code:
 
+```bash
+#!/bin/bash
+exec < /dev/tty && node_modules/.bin/git-cz --hook || true
+```
 
-## Contributing with commitizen
+We have configured three types of commits for the work on the technical reference that should reflect the amount of your contribution:
 
-This repo is designed to be used with **commitizen** for which we provide a configuration in `package.json`.
-For installing the commitizen-cli see [commitizen's repo](https://github.com/commitizen/cz-cli)
+- tr-s:     Small addition to or revision of Technical reference.
+- tr-m:     Medium addition to or revision of Technical reference.
+- tr-l:     Huge contribution to or revision of Technical reference.