Add a llava example (#47)

examples/quick_start/srt_example_llava.py

+import sglang as sgl
+
+
+@sgl.function
+def image_qa(s, image_path, question):
+    s += sgl.user(sgl.image(image_path) + question)
+    s += sgl.assistant(sgl.gen("answer"))
+
+
+runtime = sgl.Runtime(model_path="liuhaotian/llava-v1.5-7b",
+                      tokenizer_path="llava-hf/llava-1.5-7b-hf")
+sgl.set_default_backend(runtime)
+
+
+state = image_qa.run(image_path="images/cat.jpeg", question="What is this?")
+print(state["answer"])
+
+runtime.shutdown()