Examine source code of Detail Expander

{
  "manifest_version": 2,
  "name": "detail-expander",
  "version": "1.0",
  "description": "Expands contents of html <details> tags.",
  "icons": {
    "48": "icons/exp-48.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "page_action": {
    "default_icon": "icons/col.png",
    "browser_style": true
  },
  "permissions": [
    "activeTab",
    "tabs"
  ]
}