Examine source code of Custom JS Injector

{
  "manifest_version": 2,
  "name": "Custom JS Injector",
  "version": "0.0.1",
  "description": "Attach custom JavaScript to websites with an enhanced editor",
  "author": "Gchatzz",
  "permissions": [
    "activeTab",
    "storage",
    "tabs",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup/popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "options_ui": {
    "page": "options/options.html",
    "open_in_tab": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content_scripts/apply_js.js"
      ]
    }
  ],
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "content_security_policy": "script-src 'self' https://cdnjs.cloudflare.com; object-src 'self'",
  "browser_specific_settings": {
    "gecko": {
      "id": "{07398581-cbdc-446a-b713-ad5c4f2b344b}"
    }
  }
}