class8: add document link

classes/class08/meta.json

@@ -2,6 +2,6 @@
     "name": "Class 08 - Binary exploitation",
     "id": "class-08",
     "description": "The eight class focuses on binary exploitation and fuzzing. Please open the Google document provided to all registered students and follow the document.",
-    "google_doc_url": "",
+    "google_doc_url": "https://docs.google.com/document/d/1amYwna2qjWBoCX7Q5bDEGD15lMRTfORy11iBCUlzt7U/edit?usp=sharing",
     "yt_recording_url": ""
 }