Prevent autoplay on Youtube

manifest.json

{
  "manifest_version": 2,
  "name": "Prevent autoplay on Youtube",
  "description": "Prevents Youtube videos from automatically playing. You must either click the play button or press space to start the video.",
  "version": "1.0.5resigned1",
  "permissions": [
    "*://*.youtube.com/*"
  ],
  "icons": {
    "32": "youtube_html5_noauto.png"
  },
  "applications": {
    "gecko": {
      "id": "[email protected]"
    }
  },
  "content_scripts": [
    {
      "js": [
        "youtube_html5_noauto.js"
      ],
      "run_at": "document_start",
      "matches": [
        "*://*.youtube.com/*"
      ],
      "all_frames": true,
      "match_about_blank": true
    }
  ],
  "author": "Jared Stafford",
  "developer": {
    "name": "Jared Stafford",
    "url": "https://jspenguin.org/"
  }
}