Examine source code of Constant PassGen

{
  "manifest_version": 2,
  "name": "__MSG_appName__",
  "version": "1.0.1",
  "default_locale": "en",
  "description": "__MSG_appDesc__",
  "icons": {
    "48": "icons/ConstPassGen48.png",
    "96": "icons/ConstPassGen96.png"
  },
  "permissions": [
    "activeTab",
    "storage",
    "tabs"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "ConstPassGen@ext.mozilla.org",
      "strict_min_version": "57.0"
    }
  },
  "browser_action": {
    "default_icon": "icons/ConstPassGen32.png",
    "default_title": "Constant PassGen",
    "default_popup": "popup/pass_gen.html"
  }
}