Update main.py.jinja with human in the loop youtube video

src/honegumi/ax/main.py.jinja

@@ -135,6 +135,8 @@ X_train = pd.DataFrame([
 # Define y_train (normally the values would be supplied directly instead of calculating here)
 y_train = [{{ objective_function }}(row["x1"], row["x2"]{% if composition_constraint %}, row["x3"]{% endif %}{% if categorical %}, row["c1"]{% endif %}) for _, row in X_train.iterrows()]
 
+# See https://youtu.be/4tnaL9ts6CQ for simple human-in-the-loop BO instructions
+
 # Define the number of training examples
 n_train = len(X_train)
 {%- endif %}