feat: add read me

Signed-off-by: TetsuKawa <[email protected]>

system/autoware_topic_relay_controller/README.md

@@ -13,3 +13,45 @@
 ## Assumptions / Known limits
 
 TBD.
+
+# topic_relay_controller
+
+## Purpose
+The `topic_relay_controller` node subscribes to a specified topic, remaps it, and republishes it. Additionally, it has the capability to continue publishing the last received value if the subscription stops.
+
+## Inputs / Outputs
+
+### Input
+
+| Name          | Type                            | Description                                                               |
+| ------------- | ------------------------------- | ------------------------------------------------------------------------- |
+| `/<topic>`    | `<specified message type>`      | Topic to be subscribed, as defined by the `topic` parameter.              |
+| `/tf`         | `tf2_msgs::msg::TFMessage`      | (Optional) If the topic is `/tf`, used for transform message relay.       |
+| `/tf_static`  | `tf2_msgs::msg::TFMessage`      | (Optional) If the topic is `/tf_static`, used for static transforms.      |
+
+### Output
+
+| Name          | Type                            | Description                                                               |
+| ------------- | ------------------------------- | ------------------------------------------------------------------------- |
+| `/<remap_topic>` | `<specified message type>`    | Republished topic after remapping, as defined by the `remap_topic` parameter. |
+
+
+## Parameters
+- **`topic`** (string): The name of the input topic to subscribe to.
+- **`remap_topic`** (string): The name of the output topic to publish to.
+- **`topic_type`** (string): The type of messages being relayed.
+- **`qos`** (integer, default: `1`): QoS profile to use for subscriptions and publications.
+- **`transient_local`** (boolean, default: `false`): Enables transient local QoS for subscribers.
+- **`best_effort`** (boolean, default: `false`): Enables best-effort QoS for subscribers.
+- **`enable_relay_control`** (boolean, default: `true`): Allows dynamic relay control via a service.
+- **`srv_name`** (string): The service name for relay control when `enable_relay_control` is `true`.
+- **`enable_keep_publishing`** (boolean, default: `false`): Keeps publishing the last received topic value when not subscribed.
+- **`update_rate`** (integer, default: `10`): The rate (Hz) for publishing the last topic value when `enable_keep_publishing` is `true`.
+- **`frame_id`** (string, optional): Frame ID for transform messages when subscribing to `/tf` or `/tf_static`.
+- **`child_frame_id`** (string, optional): Child frame ID for transform messages when subscribing to `/tf` or `/tf_static`.
+
+## Assumptions / Known limits
+- The node assumes that the specified `topic` and `remap_topic` are valid and accessible within the ROS 2 environment.
+- If `enable_keep_publishing` is `true`, the node continuously republishes the last received value even if no new messages are being received.
+- For `/tf` and `/tf_static`, additional parameters like `frame_id` and `child_frame_id` are required for selective transformation relays.
+- QoS settings must be carefully chosen to match the requirements of the subscribed and published topics.