add labml_nn install command

Author: lakshith-403

labml_nn/lora/experiment.ipynb

@@ -1,5 +1,13 @@
 {
  "cells": [
+  {
+   "metadata": {},
+   "cell_type": "code",
+   "outputs": [],
+   "execution_count": null,
+   "source": "!pip install labml-nn",
+   "id": "c5ed37230628ee76"
+  },
   {
    "metadata": {},
    "cell_type": "code",