Update _toctree.yml

units/en/_toctree.yml

@@ -194,6 +194,10 @@
     title: Conclusion
   - local: unit8/additional-readings
     title: Additional Readings
+- title: Unit 8. Part 2 Proximal Policy Optimization (PPO) with Doom
+  sections:
+  - local: unit8/introduction-sf
+    title: Introduction
 - title: What's next? New Units Publishing Schedule
   sections:
   - local: communication/publishing-schedule