doc: Improve first installation step (#155)

Suggest to add it to Py Dev Env

README.md

@@ -51,10 +51,13 @@ sudo apt install python3-pip python3-dev python3-wheel libsodium23
 
 You can install DuniterPy and its dependencies with following command:
 
-```bash
-pip3 install duniterpy --user
+```sh
+pip install --user duniterpy
 ```
 
+Once you want to add DuniterPy to your Python project, you can add it as a dependency to your Python development environment: `pyproject.toml`, `requirements.txt`, `setup.py`.
+We recommend [Poetry](https://python-poetry.org) usage.
+
 ## Install the development environment
 
 - [Install Poetry](https://python-poetry.org/docs/#installation)