Examine source code of Reader_

{
  "manifest_version": 2,
  "name": "Reader_",
  "version": "1.0",
  "description": "Description of your extension",
  "permissions": [
    "storage",
    "activeTab",
    "downloads",
    "scripting",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "contentscript.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{8ab416f5-c4da-4665-9f2d-6428d229636c}"
    }
  }
}