feat: All heos connection commands can be chained

src/connection/heosConnection.ts

@@ -1,4 +1,4 @@
-import { HeosEventEmitter } from '../listen/responseEventHandler'
+import { HeosEventEmitter, HeosConnectionEventEmitter } from '../listen/responseEventHandler'
 import { HeosCommandAttribute } from '../types'
 import { generateHeosCommand } from '../write/heosCommand'
 
@@ -8,13 +8,19 @@ export class HeosConnection {
 		once: HeosEventEmitter,
 		socketWrite: (message: string) => any
 	) {
-		this.on = on
-		this.once = once
+		this.on = (event, listener) => {
+			on(event, listener)
+			return this
+		}
+		this.once = (event, listener) => {
+			once(event, listener)
+			return this
+		}
 		this.socketWrite = socketWrite
 	}
 
-	on: HeosEventEmitter
-	once: HeosEventEmitter
+	on: HeosConnectionEventEmitter
+	once: HeosConnectionEventEmitter
 	private socketWrite: (message: string) => any
 
 	write(

src/listen/responseEventHandler.ts

@@ -1,6 +1,12 @@
 import { HeosResponse, HeosEvent, HeosCommand } from '../types'
 import { EventEmitter } from 'events'
 import { generateHeosCommandString } from './heosCommand'
+import { HeosConnection } from '../connection/heosConnection'
+
+export type HeosConnectionEventEmitter = (
+	event: HeosCommand,
+	listener: (message: HeosResponse | HeosEvent) => void
+) => HeosConnection
 
 export type HeosEventEmitter = (
 	event: HeosCommand,