Examine source code of Opt Out

{
  "manifest_version": 2,
  "name": "Opt Out",
  "version": "1.0.4",
  "description": "Blocks offensive and inappropriate tweets.",
  "permissions": [
    "tabs",
    "webRequest",
    "webRequestBlocking",
    "activeTab",
    "storage",
    "https://api.optoutools.com/predict"
  ],
  "applications": {
    "gecko": {
      "id": "opt.out.tool@gmail.com"
    }
  },
  "browser_action": {
    "default_icon": "icons/icon-48.png",
    "default_title": "Opt-Out-Ext",
    "default_popup": "popup/popup.html"
  },
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png",
    "192": "icons/icon-192.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://twitter.com/*",
        "https://mobile.twitter.com/*"
      ],
      "css": [
        "content/opt-out.css"
      ],
      "js": [
        "content/opt-out-ext.js"
      ]
    }
  ]
}