Update helm chart README with pluginsCustomConfig flag

Author: rahulgurnani

config/charts/inferencepool/README.md

@@ -45,6 +45,25 @@ Then apply it with:
 $ helm install vllm-llama3-8b-instruct ./config/charts/inferencepool -f values.yaml
 ```
 
+### Install with Custom EPP Plugins Configuration
+
+To set custom EPP plugin config, you can pass it as an inline yaml. For example:
+
+```yaml
+  pluginsCustomConfig:
+    custom-plugins.yaml: |
+      apiVersion: inference.networking.x-k8s.io/v1alpha1
+      kind: EndpointPickerConfig
+      plugins:
+      - type: custom-scorer
+        parameters:
+          custom-threshold: 64
+      schedulingProfiles:
+      - name: default
+        plugins:
+        - pluginRef: custom-scorer
+```
+
 ### Install with Additional Ports
 
 To expose additional ports (e.g., for ZMQ), you can define them in the `values.yaml` file:
@@ -124,6 +143,7 @@ The following table list the configurable parameters of the chart.
 | `inferenceExtension.extraServicePorts`      | List of additional service ports to expose. Defaults to `[]`.                                                          |
 | `inferenceExtension.flags`                  | List of flags which are passed through to endpoint picker. Example flags, enable-pprof, grpc-port etc. Refer [runner.go](https://github.com/kubernetes-sigs/gateway-api-inference-extension/blob/main/cmd/epp/runner/runner.go) for complete list.                                                            |
 | `inferenceExtension.flags.has-enable-leader-election` | Enable leader election for high availability. When enabled, only one EPP pod (the leader) will be ready to serve traffic.       |
+| `inferenceExtension.pluginsCustomConfig`    | Custom config that is passed to EPP as inline yaml.      |
 | `provider.name`                             | Name of the Inference Gateway implementation being used. Possible values: `gke`. Defaults to `none`.                   |
 
 ## Notes