Update core and fix security issue

Author: jeromewu

package-lock.json

@@ -38,7 +38,7 @@
   },
   "homepage": "https://github.com/ffmpegjs/ffmpeg.js#readme",
   "dependencies": {
-    "@ffmpeg/core": "^0.4.0",
+    "@ffmpeg/core": "^0.6.0",
     "idb": "^4.0.5",
     "is-electron": "^2.2.0",
     "is-url": "^1.2.4",