Examine source code of cancelor

{
  "manifest_version": 2,
  "name": "cancelor",
  "version": "0.0.4",
  "author": "Jirka Justra",
  "description": "Cancel downloads automaticaly as they start. Then copy its URL to clipboard and/or send it to an external app. On/Off button included ;)",
  "applications": {
    "gecko": {
      "id": "cancelor@jirka-justra.cz"
    }
  },
  "icons": {
    "16": "cancelor.svg"
  },
  "browser_action": {
    "default_icon": {
      "16": "cancelor.svg"
    },
    "default_title": "cancelor",
    "browser_style": false
  },
  "permissions": [
    "downloads",
    "storage",
    "nativeMessaging",
    "clipboardWrite"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  }
}