Examine source code of ersci_viddown2

{
  "manifest_version": 2,
  "name": "ersci_viddown2",
  "version": "1.0",
  "icons": {
    "48": "icons/icon_48.png"
  },
  "description": "Adds right-click-context-menu which opens currently selected Youtube video link in newtab of your site",
  "background": {
    "scripts": [
      "code/background.js"
    ]
  },
  "permissions": [
    "contextMenus",
    "tabs",
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{983ffe04-3db4-4de9-b31f-3f98383141e1}"
    }
  }
}