add 'plugins' config option, new way of registering es5 plugins

js/config.js

@@ -276,6 +276,9 @@ export default {
 	hideCursorTime: 5000,
 
 	// Script dependencies to load
-	dependencies: []
+	dependencies: [],
+
+	// Plugin objects to register and use for this presentation
+	plugins: []
 
 }

js/controllers/plugins.js

@@ -20,11 +20,16 @@ export default class Plugins {
 	}
 
 	/**
-	 * Loads the dependencies of reveal.js. Dependencies are
-	 * defined via the configuration option 'dependencies'
-	 * and will be loaded prior to starting/binding reveal.js.
+	 * Loads reveal.js dependencies and registers plugins.
+	 *
+	 * Dependencies are defined via the 'dependencies' config
+	 * option and will be loaded prior to starting reveal.js.
 	 * Some dependencies may have an 'async' flag, if so they
 	 * will load after reveal.js has been started up.
+	 *
+	 * Plugins are direct references to a reveal.js plugin
+	 * object that we register and initialize after any
+	 * synchronous dependencies have loaded.
 	 */
 	load( dependencies ) {
 

js/reveal.js

@@ -145,7 +145,7 @@ export default function( revealElement, options ) {
 		window.addEventListener( 'load', layout, false );
 
 		// Load plugins then move on to #start()
-		plugins.load( config.dependencies ).then( start );
+		plugins.load( [...config.dependencies, ...config.plugins] ).then( start );
 
 		return new Promise( resolve => Reveal.on( 'ready', resolve ) );