Examine source code of Search On Npmjs

{
  "manifest_version": 2,
  "name": "Search On Npmjs",
  "description": "Search the highlighted text on Npmjs using context menu (right click).",
  "version": "0.0.1",
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "64": "icons/icon-64.png",
    "128": "icons/icon-128.png"
  },
  "web_accessible_resources": [
    "icons/*.png"
  ],
  "permissions": [
    "contextMenus",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}