Chat: add get single message

src/pages/docs/chat/rooms/messages.mdx

@@ -180,6 +180,50 @@ room.messages.send(text = "hello")
 ```
 </Code>
 
+## Get a single message <a id="get-by-serial"/>
+
+<If lang="javascript,swift,kotlin">
+Use the <If lang="javascript">[`messages.get()`](https://sdk.ably.com/builds/ably/ably-chat-js/main/typedoc/interfaces/chat-js.Messages.html#get)</If><If lang="swift">[`messages.get()`](https://sdk.ably.com/builds/ably/ably-chat-swift/main/AblyChat/documentation/ablychat/messages/get%28serial%3A%29)</If><If lang="kotlin">[`messages.get()`](https://sdk.ably.com/builds/ably/ably-chat-kotlin/main/dokka/chat-android/com.ably.chat/-messages/get.html)</If> method to get a message in a chat room.
+</If>
+
+<If lang="react">
+Use the [`getMessage()`](https://sdk.ably.com/builds/ably/ably-chat-js/main/typedoc/interfaces/chat-react.UseMessagesResponse.html#getMessage) method available from the response of the `useMessages` hook to send a message to the room:
+</If>
+
+<Code>
+```javascript
+await room.messages.get(serial);
+```
+
+```react
+import { useMessages } from '@ably/chat/react';
+
+const MyComponent = () => {
+  const { getMessage } = useMessages();
+
+  const handleMessageSend = () => {
+    getMessage(serial);
+  };
+
+  return (
+    <div>
+      <button onClick={handleMessageSend}>Send Message</button>
+    </div>
+  );
+};
+```
+
+```swift
+let message = try await room.messages.get(serial: serial)
+```
+
+```kotlin
+room.messages.get(serial = serial)
+```
+</Code>
+
+
+
 ## Update a message <a id="update"/>
 
 <Aside data-type='new'>

static/open-specs/chat.yaml

@@ -440,6 +440,85 @@ paths:
                   statusCode: 500
                   href: "https://help.ably.io/error/50001"
   /chat/{version}/rooms/{roomName}/messages/{serial}:
+    get:
+      summary: Retrieve a single message from a room
+      description: |
+        Fetches a single message from a specified room.
+      tags:
+        - rooms
+      parameters:
+        - name: version
+          in: path
+          required: true
+          description: The version of the Chat API endpoint to use.
+          schema:
+            type: string
+            example: v3
+        - name: roomName
+          in: path
+          required: true
+          description: The unique identifier of the room to fetch messages from. The `roomName` must be URI-encoded.
+          schema:
+            type: string
+        - name: serial
+          in: path
+          required: true
+          description: The unique identifier of the message to fetch. The `serial` must be URI-encoded.
+          schema:
+            type: string
+            example: "01826232498871-001@abcdefghij:001"
+        - $ref: '#/components/parameters/ClientIdHeader'
+        - $ref: '#/components/parameters/AuthorizationHeader'
+        - $ref: '#/components/parameters/AcceptHeader'
+      responses:
+        '200':
+          description: A single message retrieved from the room.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Message'
+        '400':
+          description: Invalid request.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ErrorInfo'
+        '401':
+          description: Unauthorized access.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ErrorInfo'
+              example:
+                error:
+                  message: "Unauthorized access."
+                  code: 40005
+                  statusCode: 401
+                  href: "https://help.ably.io/error/40101"
+        '404':
+          description: Message not found.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ErrorInfo'
+              example:
+                error:
+                  message: "Message not found."
+                  code: 40400
+                  statusCode: 404
+                  href: "https://help.ably.io/error/40401"
+        '500':
+          description: Server error.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ErrorInfo'
+              example:
+                error:
+                  message: "Internal server error."
+                  code: 50001
+                  statusCode: 500
+                  href: "https://help.ably.io/error/50001"
     put:
       summary: Update a message in a room
       description: |