Support clipboards with text/plain as well as file contents

ts/quill/signal-clipboard/index.ts

@@ -52,8 +52,11 @@ export class SignalClipboard {
       return;
     }
 
+    const clipboardContainsFiles = event.clipboardData.files?.length > 0;
+    if (!clipboardContainsFiles) {
       event.preventDefault();
       event.stopPropagation();
+    }
 
     const clipboardDelta = signal
       ? clipboard.convert(signal)