Examine source code of Live Expression

{
  "manifest_version": 2,
  "name": "Live Expression",
  "version": "1.0.2",
  "description": "Evaluate live expressions in browser",
  "author": "Faihan",
  "permissions": [
    "devtools"
  ],
  "icons": {
    "16": "icons/icon.svg",
    "48": "icons/icon.svg",
    "128": "icons/icon.svg"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "js/content.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "js/background.js"
    ],
    "persistent": true
  },
  "devtools_page": "html/devtools-page.html",
  "browser_specific_settings": {
    "gecko": {
      "id": "{c90bed23-e82c-4ae8-8873-38096641ffb4}"
    }
  }
}