add note to all promptfoo lectures

prompt_evaluations/07_prompt_foo_custom_graders/lesson.ipynb

@@ -6,6 +6,9 @@
    "source": [
     "# Promptfoo: custom code graders\n",
     "\n",
+    "**Note: This lesson lives in a folder that contains relevant code files. Download the entire folder if you want to follow along and run the evaluation yourself**\n",
+    "\n",
+    "\n",
     "So far we've seen how to use some of the built-in promptfoo graders like `exact-match` and `contains-all`.  Those are often useful features, but promptfoo also gives us the ability to write custom grading logic for more specific grading tasks. \n",
     "\n",
     "To demonstrate this, we'll use a very simple prompt template:\n",