Support custom extension

[ASaiAnudeep]

const config = {
  "reports": [
    {
      "targets": [
        {
          "name": "teams",
          "inputs": {
            "url": "<teams-incoming-webhook-url>"
          },
          "extensions": [
            {
              "name": "custom",
              "inputs": {
                "load": "/path/to/file" || async () => {}
              }   
            }
          ]
        }
      ],
      "results": [
        {
          "type": "testng",
          "files": ["path/to/testng-results.xml"]
        }
      ]
    }
  ]
}