feat(pdfjs-viewer): add initial PDF.js viewer assets and configuration

Add initial set of PDF.js viewer files including:
- WASM binaries for PDF rendering
- Standard fonts and CMAP files for text rendering
- UI icons and SVG assets for toolbar buttons
- TypeScript declaration files
- Loading animation GIF
- Annotation icons and UI elements

This provides the base functionality for the PDF viewer including:
- Document rendering
- Navigation controls
- Zoom functionality
- Page display options
- Annotation tools
- Document properties

public/pdfjs-viewer/images/secondaryToolbarButton-spreadNone.svg

@@ -0,0 +1,3 @@
+<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path d="M4 1.5C3.72421 1.5 3.5 1.72421 3.5 2V14C3.5 14.2758 3.72421 14.5 4 14.5H12C12.2758 14.5 12.5 14.2758 12.5 14V2C12.5 1.72421 12.2758 1.5 12 1.5H4ZM2 2C2 0.895786 2.89579 0 4 0H12C13.1042 0 14 0.895786 14 2V14C14 15.1042 13.1042 16 12 16H4C2.89579 16 2 15.1042 2 14V2Z" fill="black"/>
+</svg>