chore: Refine README, adjust image size (#88)

Signed-off-by: Ce Gao <cegao@tensorchord.ai>

Author: gaocegege

README.md

@@ -31,7 +31,9 @@ The stack is set up using [Helm](https://helm.sh/docs/), and contains the follow
 - **Request router**: Directs requests to appropriate backends based on routing keys or session IDs to maximize KV cache reuse.
 - **Observability stack**: monitors the metrics of the backends through [Prometheus](https://github.com/prometheus/prometheus) + [Grafana](https://grafana.com/)
 
- <img src="https://github.com/user-attachments/assets/8f05e7b9-0513-40a9-9ba9-2d3acca77c0c" alt="Architecture of the stack" width="800"/>
+<p align="center">
+  <img src="https://github.com/user-attachments/assets/8f05e7b9-0513-40a9-9ba9-2d3acca77c0c" alt="Architecture of the stack" width="80%"/>
+</p>
 
 ## Roadmap
 
@@ -86,16 +88,16 @@ The Grafana dashboard provides the following insights:
 6. **GPU KV Usage Percent**: Monitors GPU KV cache usage.
 7. **GPU KV Cache Hit Rate**: Displays the hit rate for the GPU KV cache.
 
- <img src="https://github.com/user-attachments/assets/05766673-c449-4094-bdc8-dea6ac28cb79" alt="Grafana dashboard to monitor the deployment" width="500"/>
+<p align="center">
+  <img src="https://github.com/user-attachments/assets/05766673-c449-4094-bdc8-dea6ac28cb79" alt="Grafana dashboard to monitor the deployment" width="80%"/>
+</p>
 
 ### Configuration
 
-See the details in `observability/README.md`
+See the details in [`observability/README.md`](./observability/README.md)
 
 ## Router
 
-### Overview
-
 The router ensures efficient request distribution among backends. It supports:
 
 - Routing to endpoints that run different models
@@ -106,6 +108,8 @@ The router ensures efficient request distribution among backends. It supports:
   - Session-ID based routing
   - (WIP) prefix-aware routing
 
+Please refer to the [router documentation](./router/README.md) for more details.
+
 ## Contributing
 
 Contributions are welcome! Please follow the standard GitHub flow: