message: Export ITelemetryPlugin for consumers to build extensions
diff: @@ -14,7 +14,8 @@ export {
  IAppInsightsCore,
  LoggingSeverity,
  _InternalMessageId,
  - ITelemetryItem
  + ITelemetryItem,
  + ITelemetryPlugin
  } from "@microsoft/applicationinsights-core-js";
  export {
  Util,
  