Add API docs for commands API

Author: AlMcKinlay

_api/commands.md

@@ -0,0 +1,35 @@
+---
+layout: documentation
+title: Commands
+description: The Commands API lets you create custom commands for users to run
+type: server
+---
+
+The Commands API lets you create custom commands for users to run
+
+## Methods
+
+### `#add(command, function)`
+
+Registers a new command for users on the lounge. `command` is what the users will type after `/`, and function is the command object. The `input` parameter on the command object will be run when the user inputs the command.
+
+### `#runAsUser(command, chatId)`
+
+Runs a command as the current user. Useful for amending messages sent, or for aliases for other commands. `command` is a string containing a standard IRC message, `chatId` is the channel or user to send the command to.
+
+#### Example
+
+```js
+const shrug = {
+  input: function(client, target, command, args) {
+    const messageWithShrug = args.join(" ").replace(/^\//, "") + " ¯\\_(ツ)_/¯";
+    client.runAsUser(messageWithShrug, target.chan.id);
+  }
+};
+
+module.exports = {
+  onServerStart(thelounge) {
+    thelounge.Commands.add("shrug", shrug);
+  }
+};
+```