Examine source code of mstc_signer

{
  "manifest_version": 2,
  "name": "mstc_signer",
  "description": "MSTC Signing App",
  "version": "1.8",
  "homepage_url": "http://www.mstcecommerce.com",
  "icons": {
    "48": "favicon.png"
  },
  "applications": {
    "gecko": {
      "id": "mstc_ecom2018@gmail.com",
      "strict_min_version": "50.0"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "favicon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "http://www.mstcecommerce.com/*",
        "https://www.mstcecommerce.com/*",
        "http://www.mstcauction.com/*",
        "https://www.mstcauction.com/*"
      ],
      "js": [
        "content-script.js"
      ]
    }
  ],
  "permissions": [
    "nativeMessaging"
  ]
}