Examine source code of Web-Encoder

{
  "manifest_version": 2,
  "name": "Web-Encoder",
  "version": "1.2.1",
  "description": "Hello Web-Encoder",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_icon": {
      "48": "icon.png"
    },
    "default_popup": "pages/popup.html"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{d125081a-51f1-492d-b374-c107a126d34c}"
    }
  }
}