Examine source code of SimplyPrint

{
  "manifest_version": 2,
  "name": "SimplyPrint",
  "description": "Send files directly to SimplyPrint",
  "version": "2.0.1",
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png",
    "256": "icons/icon256.png"
  },
  "web_accessible_resources": [
    "icons/icon.svg",
    "icons/icon.png"
  ],
  "browser_action": {
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png",
      "256": "icons/icon256.png"
    },
    "default_title": "Opening SimplyPrint",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "contact@simplyprint.io"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://*.printables.com/*"
      ],
      "js": [
        "content-scripts/printables.js"
      ]
    },
    {
      "matches": [
        "https://www.thingiverse.com/thing:*"
      ],
      "js": [
        "content-scripts/thingiverse.js"
      ]
    }
  ],
  "permissions": [
    "https://api.printables.com/*",
    "https://api.thingiverse.com/*",
    "https://simplyprint.io/*",
    "https://www.thingiverse.com/*"
  ]
}