Fix: add pixi.js/pixijs to rollup config (#13)

Author: Zyie

lib/configs/rollup.mjs

@@ -20,6 +20,8 @@ const banner = [
 ].join('\n');
 
 const builtInPackages = {
+    'pixi.js': 'PIXI',
+    pixijs: 'PIXI',
     '@pixi/accessibility': 'PIXI',
     '@pixi/app': 'PIXI',
     '@pixi/assets': 'PIXI',