feat: add example on how to use langgraph with opik for the use case of a call summarizer

Author: fschlz

integrations/langgraph/README.md

@@ -0,0 +1,17 @@
+# LangGraph Example - Call Summarizer
+
+This example demonstrates how to use LangGraph with Opik for tracing.
+
+## Setup
+
+```bash
+pyenv local 3.12
+poetry env use $(pyenv which python)
+poetry install
+```
+
+## Run
+
+```bash
+poetry run python src/call_summarizer.py
+```