Examine source code of SightCall

{
  "name": "SightCall Webextension",
  "description": "Enter the full SightCall experience thanks to this extension",
  "version": "1.6",
  "manifest_version": 2,
  "icons": {
    "16": "icon_16x16.png",
    "48": "icon_48x48.png",
    "128": "icon_128x128.png"
  },
  "applications": {
    "gecko": {
      "id": "ffwebext@sightcall.com",
      "strict_min_version": "50.0"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "nativeMessaging"
  ],
  "content_scripts": [
    {
      "js": [
        "content.js"
      ],
      "matches": [
        "https://*.sightcall.com/*",
        "https://*.rtccloud.net/*",
        "https://*.sght.io/*"
      ],
      "all_frames": true
    }
  ]
}