Add __esModule flag to improve support for cjs scripts using esModuleInterop

Author: t2t2

src/base.ts

@@ -369,3 +369,7 @@ export abstract class BaseOBSWebSocket extends EventEmitter<MapValueToArgsArray<
  */
 protected abstract decodeMessage(data: string | ArrayBuffer | Blob): Promise<IncomingMessage>;
 }
+
+// https://github.com/developit/microbundle/issues/531#issuecomment-575473024
+// eslint-disable-next-line @typescript-eslint/naming-convention
+export const __esModule = true;

src/json.ts

@@ -1,5 +1,5 @@
 import {BaseOBSWebSocket} from './base.js';
-export {OBSWebSocketError} from './base.js';
+export {__esModule, OBSWebSocketError} from './base.js';
 export type {EventTypes} from './base.js';
 import {IncomingMessage, OutgoingMessage} from './types.js';
 export * from './types.js';

src/msgpack.ts

@@ -1,6 +1,6 @@
 import {decode, encode} from '@msgpack/msgpack';
 import {BaseOBSWebSocket} from './base.js';
-export {OBSWebSocketError} from './base.js';
+export {__esModule, OBSWebSocketError} from './base.js';
 export type {EventTypes} from './base.js';
 import {IncomingMessage, OutgoingMessage} from './types.js';
 export * from './types.js';