feat: Implement sound system and toggle functionality

- Introduced SoundSystem to manage sound events using the Web Audio API.
- Added SoundEvent component to represent different sound types (e.g., coin, damage, powerup).
- Integrated sound event emissions in the Game class for various actions (e.g., collecting coins, taking damage).
- Updated UI to include a sound status indicator with toggle functionality using the 'M' key.
- Enhanced game experience with background music and sound effects for actions, improving player engagement.

This update enriches the gameplay by adding audio feedback, enhancing the overall user experience.

index.html

@@ -96,6 +96,20 @@
             z-index: 100;
             font-family: 'Courier New', monospace;
         }
+        #soundStatus {
+            position: absolute;
+            top: 20px;
+            right: 100px;
+            font-size: 20px;
+            cursor: pointer;
+            z-index: 100;
+            user-select: none;
+            opacity: 0.8;
+            transition: opacity 0.2s;
+        }
+        #soundStatus:hover {
+            opacity: 1;
+        }
         #perfMonitor {
             position: absolute;
             top: 60px;
@@ -125,6 +139,11 @@
                 top: 10px;
                 right: 10px;
             }
+            #soundStatus {
+                top: 10px;
+                right: 60px;
+                font-size: 18px;
+            }
             #perfMonitor {
                 top: 40px;
                 right: 10px;
@@ -144,6 +163,8 @@
     
     <div id="version">v<span id="versionNumber">-</span></div>
     
+    <div id="soundStatus" title="Sound ON (Press M to mute)">🔊</div>
+    
     <div id="perfMonitor">
         <div><span class="label">FPS:</span> <span id="fps">60</span></div>
         <div><span class="label">Frame:</span> <span id="frameTime">16.7</span>ms</div>
@@ -159,7 +180,7 @@
     
     <div id="instructions">
         <p><strong>Controls:</strong> WASD or Arrow Keys to move | Touch and drag to move (mobile) | Collect yellow coins | Avoid red obstacles!</p>
-        <p style="margin-top: 5px; font-size: 11px; opacity: 0.7;">Press "T" or shake device to toggle performance monitor</p>
+        <p style="margin-top: 5px; font-size: 11px; opacity: 0.7;">Press "T" to toggle performance monitor | Press "M" to toggle sound</p>
     </div>
 
     <script type="module">