Document setup for previewing documentation locally

documentation.md

@@ -30,6 +30,15 @@ In doing documentation we are living our [values](values) of encouraging continu
 
 ## Local preview
 
+### Setup
+
+```bash
+sudo apt install python3-sphinx
+pip3 install -r requirements.txt
+```
+
+### Generating
+
 Running this documentation locally:
 
 ```bash