build: clear jupyter notebook outputs on clean task

- Clear jupyter notebook output on clean target
- Clear jupyter notebook run counter on clean target
- Fix: Deletion of lib/ if lib/ does not exist

Makefile

@@ -82,8 +82,9 @@ clean:
 	rm -f src/*.pyc
 	rm -f src/*.mpy
 	rm -f $(JUPYTER_PYTHON_FILES)
-	rm -r lib/
+	rm -rf lib/
 	rm -f requirements.txt
+	$(VENV) jupyter nbconvert --clear-output --inplace src/*.ipynb
 
 env:
 	poetry install