Add SDB Audio Extractor extension with options and popup UI

- Implemented manifest.json for extension configuration
- Created options.html and options.js for user settings management
- Developed popup.html and popup.js for audio extraction functionality
- Added icons for the extension (icon16.png, icon48.png)
- Integrated API token and base URL configuration with validation
- Implemented audio extraction from YouTube videos with error handling

icon.svg

@@ -0,0 +1,25 @@
+<svg width="48" height="48" viewBox="0 0 48 48" xmlns="http://www.w3.org/2000/svg">
+  <!-- Background circle -->
+  <circle cx="24" cy="24" r="22" fill="#ff0000"/>
+
+  <!-- Musical note -->
+  <g fill="#ffffff">
+    <!-- Note head -->
+    <ellipse cx="14" cy="33" rx="4" ry="3"/>
+
+    <!-- Note stem -->
+    <rect x="18" y="14" width="2" height="19"/>
+
+    <!-- Note flag -->
+    <path d="M20 14 Q28 10 26 18 L20 16 Z"/>
+  </g>
+
+  <!-- Download arrow -->
+  <g fill="#ffffff">
+    <!-- Arrow shaft -->
+    <rect x="30" y="20" width="2" height="8"/>
+
+    <!-- Arrow head -->
+    <path d="M27 26 L31 32 L35 26 Z"/>
+  </g>
+</svg>