Examine source code of Nimbus Capture

{
  "manifest_version": 2,
  "name": "Nimbus Capture",
  "version": "1.0",
  "description": "Capture, edit, and annotate screenshots easily.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{91ebd1dc-5c41-448b-a5d7-836666c9806e}"
    }
  }
}