Examine source code of WebNotepad

{
  "manifest_version": 2,
  "name": "WebNotepad",
  "version": "1.5.2resigned1",
  "description": "A simple notepad for Firefox",
  "homepage_url": "https://jaroslavc.eu/webnotepad/",
  "icons": {
    "600": "img/webnotepad.png"
  },
  "browser_action": {
    "default_icon": "img/webnotepad.png",
    "default_title": "WebNotepad",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "webnotepad-dev@jaroslavc.eu"
    }
  }
}