Add doc for feature support matrix

Author: chang-l

docs/source/reference/multimodal-feature-support-matrix.md

@@ -0,0 +1,13 @@
+# Multimodal Feature Support Matrix (PyTorch Backend)
+
+| Model              | CUDA Graph | IFB w/ SharedTensor | KV Cache Reuse | Chunked Prefill |
+| :----------------- | :--------- | :------------------ | :------------- | :-------------- |
+| Gemma 3            | Yes        | Yes                 | No             | No              |
+| HyperCLOVA         | Yes        | Yes                 | No             | No              |
+| VILA               | Yes        | No                  | No             | No              |
+| LLaVA-NeXT         | Yes        | No                  | No             | No              |
+| Llama 4            | Yes        | No                  | No             | No              |
+| Mistral            | Yes        | Yes                 | No             | No              |
+| Phi-4-multimodal   | Yes        | Yes                 | No             | No              |
+| Qwen2-VL           | Yes        | Yes                 | Yes            | No              |
+| Qwen2.5-VL         | Yes        | Yes                 | Yes            | No              |