Examine source code of Fire Page Editing

{
  "manifest_version": 2,
  "name": "Fire Page Editing",
  "version": "2.0",
  "description": "Inject HTML, CSS or JavaScript into any web-page. The changes you make are applied everytime you visit the specified website(s).",
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "browser_action": {
    "default_icon": "icons/icon16.png",
    "default_popup": "popup.html",
    "default_title": "Rapid Page Editor"
  },
  "background": {
    "scripts": [
      "eventpage.js"
    ],
    "persistent": false
  },
  "applications": {
    "gecko": {
      "id": "{fb08f1c9-d0c0-4537-9de9-ddd478e2f490}",
      "strict_min_version": "57.0"
    }
  },
  "content_scripts": [
    {
      "run_at": "document_start",
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "content.css"
      ],
      "match_about_blank": true
    }
  ],
  "permissions": [
    "storage",
    "activeTab",
    "contextMenus",
    "unlimitedStorage"
  ]
}