Examine source code of Know TLS Cert

{
  "name": "Know TLS Cert",
  "description": "Show TLS cert info",
  "manifest_version": 2,
  "version": "0.2.0",
  "homepage_url": "https://garywill.github.io",
  "developer": {
    "name": "Garywill",
    "url": "https://github.com/garywill/know-tls-cert"
  },
  "icons": {
    "512": "icon.png"
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "*://*/*",
    "notifications"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c8b00a91-47c4-43a5-b839-3bb786564ae4}"
    }
  }
}