feat(demo): add LED labels

Author: urish

demo/src/index.html

@@ -11,8 +11,8 @@
     <h2>AVR8js LED Demo</h2>
     <div class="app-container">
       <div class="leds">
-        <wokwi-led color="green"></wokwi-led>
-        <wokwi-led color="red"></wokwi-led>
+        <wokwi-led color="green" label="13"></wokwi-led>
+        <wokwi-led color="red" label="12"></wokwi-led>
       </div>
       <div class="toolbar">
         <button id="run-button">Run</button>