feat: implement PDF attachment extraction functionality with web worker support

- Added a new worker script to handle extraction of embedded attachments from PDF files.
- Created TypeScript definitions for the message structure and response types.
- Updated the main extraction logic to utilize the worker for improved performance and responsiveness.
- Integrated the extraction feature into the UI, allowing users to extract attachments as a ZIP file.
- Enhanced error handling and user feedback during the extraction process.

public/workers/extract-attachments.worker.d.ts

@@ -0,0 +1,19 @@
+declare const coherentpdf: typeof import('../../src/types/coherentpdf.global').coherentpdf;
+
+interface ExtractAttachmentsMessage {
+  command: 'extract-attachments';
+  fileBuffers: ArrayBuffer[];
+  fileNames: string[];
+}
+
+interface ExtractAttachmentSuccessResponse {
+  status: 'success';
+  attachments: Array<{ name: string; data: ArrayBuffer }>;
+}
+
+interface ExtractAttachmentErrorResponse {
+  status: 'error';
+  message: string;
+}
+
+type ExtractAttachmentResponse = ExtractAttachmentSuccessResponse | ExtractAttachmentErrorResponse;