Feature/vllm/input embedding completion api (#17590)

Signed-off-by: Andrew Sansom <andrew@protopia.ai>
Signed-off-by: Nan2018 <nan@protopia.ai>
Co-authored-by: 临景 <linjing.yx@alibaba-inc.com>
Co-authored-by: Bryce1010 <bryceyx@gmail.com>
Co-authored-by: Andrew Sansom <andrew@protopia.ai>
Co-authored-by: Andrew Sansom <qthequartermasterman@gmail.com>
Co-authored-by: Cyrus Leung <cyrus.tl.leung@gmail.com>

docs/source/index.md

@@ -119,6 +119,7 @@ serving/offline_inference
 serving/openai_compatible_server
 serving/serve_args
 serving/multimodal_inputs
+serving/prompt_embeds
 serving/distributed_serving
 serving/metrics
 serving/engine_args