generate stream without promise

streams are already async, and don't need to be wrapped in a promise.

src/index.ts

@@ -2,6 +2,7 @@
 
 import { launch, LaunchedChrome } from 'chrome-launcher';
 import * as CDP from 'chrome-remote-interface';
+import { Readable, Stream } from 'stream';
 
 import { ChromePrintOptions } from './ChromePrintOptions';
 import * as CompletionTrigger from './CompletionTrigger';
@@ -86,6 +87,20 @@ async function generate(html: string, options: CreateOptions): Promise<CreateRes
   }
 }
 
+function generateToStream(html: string, options: CreateOptions): Stream {
+  const stream = new Readable();
+  (async () => {
+    try {
+      const result = await generate(html, options);
+      stream.push(result.toBase64(), 'base64');
+      stream.push(null);
+    } catch (e) {
+      stream.emit('error', e);
+    }
+  })();
+  return stream;
+}
+
 /**
  * Throws an exception if the operation has been canceled.
  *