Examine source code of Cleanit

{
  "manifest_version": 2,
  "name": "Cleanit",
  "version": "1.0.4resigned1",
  "homepage_url": "https://github.com/Spriteware/cleanit",
  "applications": {
    "gecko": {
      "id": "cleanit@franpapers.com"
    }
  },
  "description": "Allows fast deletion of unconvenient HTML elements.",
  "icons": {
    "48": "border-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_start",
      "js": [
        "cleanit.js"
      ]
    }
  ]
}