Examine source code of Productive Twitter

{
  "manifest_version": 2,
  "name": "Productive Twitter",
  "version": "1.0.0",
  "description": "Minimal and friendly theme for productive social sharing",
  "short_name": "Productive Twitter",
  "permissions": [
    "activeTab",
    "declarativeContent",
    "tabs"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://twitter.com/*"
      ],
      "css": [
        "override.css"
      ],
      "js": [
        "override.js"
      ]
    }
  ],
  "page_action": {
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png"
    }
  }
}