ImportSongs: Add plugin support

- Files with filenames that end with .taikoweb.js can be imported and run to add custom functionality to the game
- The plugin file is a javascript module script that should have a class in the default export
- Currently supported methods in the class: name (string), load, start, stop, unload (functions)
- The class can be extended from the Patch class to add automatic patching of variables and functions
- Here are some of the plugins I made: https://github.com/KatieFrogs/taiko-web-plugins

public/src/js/assets.js

@@ -36,7 +36,8 @@ var assets = {
 		"lyrics.js",
 		"customsongs.js",
 		"abstractfile.js",
-		"idb.js"
+		"idb.js",
+		"plugins.js"
 	],
 	"css": [
 		"main.css",