Examine source code of Environment Indicator

{
  "name": "Environment Indicator",
  "description": "Add an environment marker to differentiate QA environments from production. In addition, you can create your own indicator rules",
  "version": "1.0.5",
  "manifest_version": 2,
  "default_locale": "en",
  "icons": {
    "16": "icons/icon-16x16.png",
    "48": "icons/icon-48x48.png",
    "128": "icons/icon-128x128.png"
  },
  "permissions": [
    "storage",
    "http://*/*",
    "https://*/*"
  ],
  "content_security_policy": "script-src 'self'; object-src 'self';",
  "web_accessible_resources": [
    "icons/icon-16x16.png",
    "icons/icon-48x48.png",
    "icons/icon-128x128.png",
    "www/index.html",
    "assets/content.css",
    "my-content-script.js",
    "background.js"
  ],
  "browser_action": {
    "default_popup": "www/index.html#/popup",
    "default_title": "Environment Indicator",
    "default_icon": {
      "16": "icons/icon-16x16.png",
      "48": "icons/icon-48x48.png",
      "128": "icons/icon-128x128.png"
    }
  },
  "options_page": "www/index.html",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "css": [
        "assets/content.css"
      ],
      "js": [
        "my-content-script.js"
      ],
      "run_at": "document_end"
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "short_name": "__MSG_extensionName__",
  "browser_specific_settings": {
    "gecko": {
      "id": "{246ac5ce-0365-422a-821d-5eaf3bc9c7c9}"
    }
  }
}