Added missing "plugins" member for video.js PlayerOptions

This is documented for step 3 on http://docs.videojs.com/docs/guides/plugins.html

types/video.js/index.d.ts

@@ -3,6 +3,7 @@
 // Definitions by: Vincent Bortone <https://github.com/vbortone>
 //                 Simon Clériot <https://github.com/scleriot>
 //                 Sean Bennett <https://github.com/SWBennett06>
+//                 Christoph Wagner <https://github.com/IgelCampus>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
 // The Video.js API allows you to interact with the video through
@@ -33,6 +34,7 @@ declare namespace videojs {
 		fluid?: boolean;
 		language?: string;
 		notSupportedMessage?: string;
+		plugins?: any;
 	}
 
 	interface Source {