docs: initial state constructor option

Author: MatthewWid

docs/api.md

@@ -41,6 +41,7 @@ Note that creating a new session will immediately send the initial status code a
 |`keepAlive`|`number` \| `null`|`10000`|Time in milliseconds interval for the session to send a comment to keep the connection alive.<br><br>Give as `null` to disable the keep-alive mechanism.|
 |`statusCode`|`number`|`200`|Status code to be sent to the client.<br><br>Event stream requests can be redirected using HTTP 301 and 307 status codes. Make sure to set `Location` header when using these status codes (301/307) using the `headers` property.<br><br>A client can be asked to stop reconnecting by send a 204 status code.|
 |`headers`|`object`|`{}`|Additional headers to be sent along with the response.|
+|`state`|`object`|`{}`|Initial custom state for the session.<br><br>Accessed via the [`state`](#sessionstate-state) property.<br><br>When using TypeScript, providing the initial state structure allows the type of the `state` property to be automatically inferred.|
 
 #### `Session#lastId`: `string`
 
@@ -174,7 +175,13 @@ A `Channel` is used to broadcast events to many sessions at once.
 You may use the second generic argument `SessionState` to enforce that only sessions
 with the same state type may be registered with this channel.
 
-#### `new Channel<State, SessionState>()`
+#### `new Channel<State, SessionState>([options = {}])`
+
+`options` is an object with the following properties:
+
+|Property|Type|Default|Description|
+|-|-|-|-|
+|`state`|`object`|`{}`|Initial custom state for the channel.<br><br>Accessed via the [`state`](#channelstate-state) property.<br><br>When using TypeScript, providing the initial state structure allows the type of the `state` property to be automatically inferred.|
 
 #### `Channel#state`: `State`