feat: add JSON to PDF and PDF to JSON conversion tools

- Introduced new pages and logic for converting JSON files to PDF and vice versa.
- Implemented web workers for handling conversion processes in the background.
- Updated Vite configuration to include new HTML pages for the conversion tools.
- Enhanced user interface with file upload sections and status messages for conversion progress.
- Added TypeScript definitions for worker communication and response handling.

public/workers/json-to-pdf.worker.js

@@ -0,0 +1,63 @@
+self.importScripts('/coherentpdf.browser.min.js');
+
+function convertJSONsToPDFInWorker(fileBuffers, fileNames) {
+  try {
+    const pdfFiles = [];
+    const transferBuffers = [];
+
+    for (let i = 0; i < fileBuffers.length; i++) {
+      const buffer = fileBuffers[i];
+      const fileName = fileNames[i];
+      const uint8Array = new Uint8Array(buffer);
+
+      let pdf;
+      try {
+        pdf = coherentpdf.fromJSONMemory(uint8Array);
+      } catch (error) {
+        const errorMsg = error && error.message 
+          ? error.message 
+          : 'Unknown error';
+        throw new Error(
+          `Failed to convert "${fileName}" to PDF. ` +
+          `The JSON file must be in the format produced by cpdf's outputJSONMemory. ` +
+          `Error: ${errorMsg}`
+        );
+      }
+      
+      const pdfData = coherentpdf.toMemory(pdf, false, false);
+
+      const pdfBuffer = pdfData.buffer.slice(0);
+      pdfFiles.push({
+        name: fileName,
+        data: pdfBuffer,
+      });
+      transferBuffers.push(pdfBuffer);
+
+      coherentpdf.deletePdf(pdf);
+    }
+
+    self.postMessage(
+      {
+        status: 'success',
+        pdfFiles: pdfFiles,
+      },
+      transferBuffers
+    );
+  } catch (error) {
+    self.postMessage({
+      status: 'error',
+      message:
+        error instanceof Error
+          ? error.message
+          : 'Unknown error during JSON to PDF conversion.',
+    });
+    return;
+  }
+}
+
+self.onmessage = (e) => {
+  if (e.data.command === 'convert') {
+    convertJSONsToPDFInWorker(e.data.fileBuffers, e.data.fileNames);
+  }
+};
+