[Lora][Frontend]Add default local directory LoRA resolver plugin. (#16855)

Signed-off-by: jberkhahn <jaberkha@us.ibm.com>

docs/source/features/lora.md

@@ -159,9 +159,12 @@ Alternatively, you can use the LoRAResolver plugin to dynamically load LoRA adap
 
 You can set up multiple LoRAResolver plugins if you want to load LoRA adapters from different sources. For example, you might have one resolver for local files and another for S3 storage. vLLM will load the first LoRA adapter that it finds.
 
-You can either install existing plugins or implement your own.
+You can either install existing plugins or implement your own. By default, vLLM comes with a [resolver plugin to load LoRA adapters from a local directory.](https://github.com/vllm-project/vllm/tree/main/vllm/plugins/lora_resolvers)
+To enable this resolver, set `VLLM_ALLOW_RUNTIME_LORA_UPDATING` to True, set `VLLM_PLUGINS` to include `lora_filesystem_resolver`, and then set `VLLM_LORA_RESOLVER_CACHE_DIR` to a local directory. When vLLM receives a request using a LoRA adapter `foobar`,
+it will first look in the local directory for a directory `foobar`, and attempt to load the contents of that directory as a LoRA adapter. If successful, the request will complete as normal and
+that adapter will then be available for normal use on the server.
 
-Steps to implement your own LoRAResolver plugin:
+Alternatively, follow these example steps to implement your own plugin:
 1. Implement the LoRAResolver interface.
 
     Example of a simple S3 LoRAResolver implementation: