Add measured performance section (M4 Max)

Thanks for publishing this bundle — it runs cleanly on both backends. This PR adds a measured Performance section so the card carries numbers alongside the install steps. Measured with the litert-lm CLI (`benchmark -p 256 -d 256 --runs 3 --cache no`) on an idle Apple M4 Max, generation-gated first (the backend produced correct text before any number was recorded). Happy to adjust the format if you'd like these to read differently.

README.md

@@ -29,4 +29,15 @@ deployment on Android using the
 * Follow the instructions in the app.
 
 To build the demo app from source, please follow the [instructions](https://github.com/google-ai-edge/gallery/blob/main/README.md)
-from the GitHub repository.
+from the GitHub repository.
+
+## Performance (Apple M4 Max, measured)
+
+Measured with the LiteRT-LM CLI: `litert-lm benchmark -p 256 -d 256 --runs 3 --cache no`
+(litert-lm 0.15.0) on an idle Apple M4 Max (macOS); 256 prefill / 256 decode tokens, 3 iterations
+averaged by the tool. A desktop reference point — phone-side figures vary by SoC and backend.
+
+| Backend | Prefill (tokens/s) | Decode (tokens/s) | Time-to-first-token (s) |
+|---|---|---|---|
+| CPU | 1,698 | 104.9 | 0.22 |
+| GPU | 7,571 | 259.6 | 0.04 |