Examine source code of DBBlocker

{
  "manifest_version": 2,
  "name": "DBBlocker",
  "version": "1",
  "description": "WebPageBlocker",
  "icons": {
    "48": "icons/blocker-48.png"
  },
  "permissions": [
    "storage",
    "tabs"
  ],
  "browser_action": {
    "default_icon": {
      "32": "icons/blocker-32.png"
    },
    "default_title": "DBBlocker",
    "default_popup": "popup/popup.html"
  },
  "background": {
    "scripts": [
      "blocker.js"
    ]
  },
  "applications": {
    "gecko": {
      "id": "dbakalis@extraline.gr"
    }
  }
}