add unit to tree and readme

README.md

@@ -18,6 +18,7 @@ You can access the course here 👉 <a href="https://hf.co/learn/agents-course"
 | 1    | [Introduction to Agents](https://huggingface.co/learn/agents-course/en/unit1/introduction)       | Definition of agents, LLMs, model family tree, and special tokens.          |
 | 1.5    | [(Bonus Unit 1) Fine-tuning an LLM for Function-calling](https://huggingface.co/learn/agents-course/bonus-unit1/introduction)       | Learn to fine-tune an LLM for Function-Calling |
 | 2    | [2_frameworks](units/en/unit2/README.md)                     | Overview of smolagents, LangChain, LangGraph, and LlamaIndex.               |
+| 2.5  | [(Bonus Unit 2) Observability and Evaluation](https://huggingface.co/learn/agents-course/bonus-unit2/introduction) | Learn how to trace and evaluate your agents.
 | 3    | [3_use_cases](units/en/unit3/README.md)                      | SQL, code, retrieval, and on-device agents using various frameworks.        |
 | 4    | [4_final_assignment_with_benchmark](units/en/unit4/README.md) | Automated evaluation of agents and leaderboard with student results.        |
 

units/en/_toctree.yml

@@ -102,6 +102,14 @@
     title: Let's Fine-Tune your model for Function-calling
   - local: bonus-unit1/conclusion
     title: Conclusion
+- title: Bonus Unit 2. Agent Observability and Evaluation
+  sections:
+  - local: bonus-unit2/introduction
+    title: Introduction
+  - local: bonus-unit2/what-is-agent-observability-and-evaluation
+    title: What is agent observability and evaluation?
+  - local: bonus-unit2/quiz
+    title: Quiz
 - title: When the next steps are published?
   sections:
   - local: communication/next-units