Examine source code of MuteTab

{
  "manifest_version": 2,
  "name": "MuteTab",
  "version": "0.0.3resigned1",
  "description": "",
  "applications": {
    "gecko": {
      "id": "mutetab@mozilla.org",
      "strict_min_version": "45.0"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}