🎨 add cross-reference to api doc and print docstring

Author: enryH

docs/tutorial/tutorial.ipynb

@@ -65,7 +65,9 @@
    "id": "076361ca",
    "metadata": {},
    "source": [
-    "Inspect the signature."
+    "Inspect the signature. In an interactive session you could also use `hello_world?` to\n",
+    "display the docstring. See the rendered version here:\n",
+    "[reference/python_package.mockup](python_package.mockup.hello_world)"
    ]
   },
   {
@@ -75,7 +77,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "hello_world?"
+    "help(hello_world)"
    ]
   },
   {

docs/tutorial/tutorial.py

@@ -23,10 +23,12 @@
 print(ret)
 
 # %% [markdown]
-# Inspect the signature.
+# Inspect the signature. In an interactive session you could also use `hello_world?` to
+# display the docstring. See the rendered version
+# [of `hello_world` under the Reference]](python_package.mockup.hello_world)
 
 # %%
-# hello_world?
+help(hello_world)
 
 # %% [markdown]
 # Simple example for a recipe showing what the package can do.