doc: Add documentation to contribute

CONTRIBUTING.md

@@ -4,6 +4,21 @@ If you learn something useful, please add it to this file.
 
 # Run the test suite
 
-```
+```sh
 python -m unittest
 ```
+
+# Build the docs
+
+```sh
+pip install -U sphinx furo
+
+meson -Ddocs=true build
+# or
+meson --reconfigure -Ddocs=true build
+
+ninja -C build docs/en
+
+python -m http.server 2310 --bind 127.0.0.1 --directory build/docs/en/
+xdg-open http://127.0.0.1:2310/
+```