feat: Add Digital Signature and Validate Signature tools

New Features:
- Digital Signature tool: Sign PDFs with X.509 certificates (PFX/PEM)
  - Visible and invisible signatures
  - All pages, first page, last page, or custom page selection
  - Dynamic signature height based on text content
  - Custom signature text, image, and styling options

- Validate Signature tool: Verify digital signatures in PDFs
  - Extract and parse PKCS#7 signatures
  - View signer and issuer certificate details
  - Check certificate validity and expiry
  - Optional custom X.509 certificate for trust verification
  - Full/partial coverage detection

Infrastructure:
- Added Cloudflare Worker CORS proxy for certificate chain fetching
- Updated README with new tools and proxy deployment instructions

Documentation:
- Added Digital Signature and Validate Signature to README tools table
- Added CORS proxy deployment guide for self-hosters

src/js/const/cdn-version.ts

@@ -1,11 +1,9 @@
 export const PACKAGE_VERSIONS = {
-    libreoffice: '2.3.1', 
-    ghostscript: '0.1.0', 
-    pymupdf: '0.1.9', 
+    ghostscript: '0.1.0',
+    pymupdf: '0.1.9',
 } as const;
 
 export const CDN_URLS = {
-    libreoffice: `https://cdn.jsdelivr.net/npm/@bentopdf/libreoffice-wasm@${PACKAGE_VERSIONS.libreoffice}/assets/`,
     ghostscript: `https://cdn.jsdelivr.net/npm/@bentopdf/gs-wasm@${PACKAGE_VERSIONS.ghostscript}/assets/`,
     pymupdf: `https://cdn.jsdelivr.net/npm/@bentopdf/pymupdf-wasm@${PACKAGE_VERSIONS.pymupdf}/assets/`,
 } as const;