feat: Add PDF viewer and preview components with styling and functionality

- Implemented DeesPdfViewer for full-featured PDF viewing with toolbar and sidebar navigation.
- Created DeesPdfPreview for lightweight PDF previews.
- Introduced PdfManager for managing PDF document loading and caching.
- Added CanvasPool for efficient canvas management.
- Developed utility functions for performance monitoring and file size formatting.
- Established styles for viewer and preview components to enhance UI/UX.
- Included demo examples for showcasing PDF viewer capabilities.

ts_web/elements/dees-pdf-viewer/demo.ts

@@ -0,0 +1,69 @@
+import { html } from '@design.estate/dees-element';
+
+export const demo = () => html`
+  <style>
+    .demo-container {
+      padding: 40px;
+      background: #f5f5f5;
+    }
+
+    .demo-section {
+      margin-bottom: 40px;
+    }
+
+    h3 {
+      margin-bottom: 20px;
+      font-size: 18px;
+      font-weight: 600;
+    }
+
+    dees-pdf-viewer {
+      border: 1px solid #ddd;
+      border-radius: 8px;
+      overflow: hidden;
+    }
+
+    .viewer-tall {
+      height: 800px;
+    }
+
+    .viewer-compact {
+      height: 500px;
+    }
+  </style>
+
+  <div class="demo-container">
+    <div class="demo-section">
+      <h3>Full Featured PDF Viewer with Toolbar</h3>
+      <dees-pdf-viewer
+        class="viewer-tall"
+        pdfUrl="https://raw.githubusercontent.com/mozilla/pdf.js/ba2edeae/web/compressed.tracemonkey-pldi-09.pdf"
+        showToolbar="true"
+        showSidebar="false"
+        initialZoom="page-fit"
+      ></dees-pdf-viewer>
+    </div>
+
+    <div class="demo-section">
+      <h3>PDF Viewer with Sidebar Navigation</h3>
+      <dees-pdf-viewer
+        class="viewer-tall"
+        pdfUrl="https://raw.githubusercontent.com/mozilla/pdf.js/ba2edeae/web/compressed.tracemonkey-pldi-09.pdf"
+        showToolbar="true"
+        showSidebar="true"
+        initialZoom="page-width"
+      ></dees-pdf-viewer>
+    </div>
+
+    <div class="demo-section">
+      <h3>Compact Viewer without Controls</h3>
+      <dees-pdf-viewer
+        class="viewer-compact"
+        pdfUrl="https://raw.githubusercontent.com/mozilla/pdf.js/ba2edeae/examples/learning/helloworld.pdf"
+        showToolbar="false"
+        showSidebar="false"
+        initialZoom="auto"
+      ></dees-pdf-viewer>
+    </div>
+  </div>
+`;