Examine source code of Forekast

{
  "manifest_version": 3,
  "name": "Forekast",
  "description": "The Calendar of the Internet",
  "version": "1.0",
  "icons": {
    "16": "forekast_icon_16x16.png",
    "32": "forekast_icon_32x32.png",
    "48": "forekast_icon_48x48.png",
    "128": "forekast_icon_128x128.png"
  },
  "action": {
    "default_popup": "index.html",
    "default_icon": "forekast_extension.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "forekastdev@gmail.com"
    }
  }
}