docs(readme): Minor spelling fix (obs-websocket-community-projects#169)

Author: jwulf

README.md

@@ -58,7 +58,7 @@ All requests support the following two Syntax options where both `err` and `data
 _Note that all response objects will supply both the original [obs-websocket][link-obswebsocket] response items in their original format (ex: `'response-item'`), but also camelCased (ex: `'responseItem'`) for convenience._  
 - RequestName must exactly match what is defined by the [`obs-websocket`][link-obswebsocket] plugin.  
 - `{args}` are optional. Note that both `request-type` and `message-id` will be bound automatically.  
-- To use callbacks instead of promises, use the `sendCallback` method insetad of `send`.
+- To use callbacks instead of promises, use the `sendCallback` method instead of `send`.
 
 ```js
 // Promise API