Examine source code of Close current Tab dark

{
  "manifest_version": 2,
  "name": "Close current Tab",
  "version": "1.2",
  "author": "Bruno Lacombe",
  "description": "Add a button to close the current active tab.",
  "icons": {
    "48": "icons/close.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "16": "icons/close.png",
      "32": "icons/close.png",
      "48": "icons/close.png"
    }
  }
}