Examine source code of Environment Switcher

{
  "manifest_version": 2,
  "name": "Environment Switcher",
  "description": "Quickly switch project pages between environments",
  "version": "0.2.2",
  "short_name": "Env Switch",
  "icons": {
    "16": "icon/16.png",
    "32": "icon/32.png",
    "48": "icon/48.png",
    "64": "icon/64.png",
    "96": "icon/96.png",
    "128": "icon/128.png",
    "256": "icon/256.png"
  },
  "permissions": [
    "storage",
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "extension@environment-switcher.xyz"
    }
  },
  "browser_action": {
    "default_title": "Environment Switcher",
    "default_popup": "popup.html"
  }
}