FFM-8890 Update readme

README.md

@@ -137,7 +137,6 @@ config :cfclient,
 ## Set logging level
 Optionally you may set the required log level of the SDK. If not provided, the SDK will default to `warning`.
 
-
 #### Elixir logging configuration example
 ```elixir
 config :cfclient,
@@ -209,6 +208,29 @@ config :cfclient,
     ]}]
 ```
 
+## Experimental: Use Flag Identifier with Percentage Rollout Hash
+
+### Elixir
+
+To enable this, set `hash_flag_and_target_ids` to true.
+
+If `hash_flag_and_target_ids` is not explicitly set, or set to false, the SDK will use the original hashing method.
+
+```elixir
+    log_level: :debug,
+    verbose_evaluation_logs: true,
+    [api_key: System.get_env("FF_API_KEY_0"),
+    # For additional config you can pass in, see Erlang SDK docs: https://github.com/harness/ff-erlang-server-sdk/blob/main/docs/further_reading.md#further-reading
+    # we are just using the main config url here as an example.
+    config: [
+      config_url: "https://config.ff.harness.io/api/1.0",
+      events_url: "https://events.ff.harness.io/api/1.0",
+      poll_interval: 60000,
+      analytics_enabled: true,
+      hash_flag_and_target_ids: true
+    ]]
+```
+
 ## Run multiple instances of the SDK
 
 The SDK by default starts up a single instance called `default` which is configured with your project API key.