Examine source code of External Video

{
  "manifest_version": 2,
  "name": "External Video",
  "version": "1.5resigned1",
  "description": "Opens video link in MPV",
  "homepage_url": "https://github.com/vayan/external-video",
  "applications": {
    "gecko": {
      "id": "external-video@yan.pm",
      "strict_min_version": "50.0"
    }
  },
  "icons": {
    "48": "icons/logo-48.png"
  },
  "background": {
    "scripts": [
      "external-video.js"
    ]
  },
  "options_ui": {
    "page": "settings/options.html"
  },
  "permissions": [
    "nativeMessaging",
    "webRequestBlocking",
    "webRequest",
    "storage",
    "contextMenus",
    "history",
    "*://*.youtube.com/watch*",
    "*://*.vimeo.com/*",
    "*://*.streamable.com/*",
    "*://*.liveleak.com/view*",
    "*://*.vid.me/*",
    "*://*.funnyordie.com/videos/*",
    "*://*.dailymotion.com/video/*"
  ]
}