Examine source code of Address bar math

{
  "manifest_version": 2,
  "name": "Address bar math",
  "author": "Benjamin Cooper",
  "version": "1.2",
  "applications": {
    "gecko": {
      "id": "address-bar-math@benc.io"
    }
  },
  "description": "Do super fast math in the address bar with support for all sorts of functions!",
  "omnibox": {
    "keyword": "m@"
  },
  "background": {
    "scripts": [
      "index.js"
    ]
  }
}