docs: add concise API server endpoint guide (#6114)

Signed-off-by: Hongsheng Liu <liuhongsheng4@huawei.com>
Co-authored-by: hsliu_ustc <hsliu_ustc@noreply.gitcode.com>

docs/examples/README.md

@@ -3,4 +3,6 @@
 vLLM-Omni's examples are split into two categories:
 
 - If you are using vLLM-Omni from within Python code, see the *Offline Inference* section.
-- If you are using vLLM-Omni from an HTTP application or client, see the *Online Serving* section.
+- If you are using vLLM-Omni from an HTTP application or client, start with
+  the [API Server guide](../serving/README.md) to choose an endpoint, then use
+  the *Online Serving* section for model-specific examples.