Examine source code of Hide Subscription Videos

{
  "manifest_version": 2,
  "name": "Hide Subscription Videos",
  "description": "Hide certain videos from your Subscription feed based on keywords in a video's title",
  "version": "1.0.4",
  "icons": {
    "256": "icons/extLogo.png"
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "hideSubscriptionVideos@fake-hideSubscriptionVideos.com"
    }
  },
  "content_scripts": [
    {
      "run_at": "document_end",
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "app.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": "icons/extLogo.png",
    "default_title": "Hide Subscription Videos",
    "default_popup": "popup/view.html"
  }
}