Examine source code of TrackYourTime

{
  "author": "Defend.pw",
  "manifest_version": 2,
  "name": "TrackYourTime 2",
  "version": "1.0",
  "description": "Time tracker extension",
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ]
    }
  ],
  "icons": {
    "128": "icon.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "<all_urls>",
    "tabs",
    "storage"
  ]
}