Add keyboard support to webrtc

Bug: 141887532
Test: launch_cvd --start_webrtc
Change-Id: Ia7847a0e0f1df557e7922a48bbad999a971e3ef4
diff --git a/host/frontend/gcastv2/webrtc/assets/index.html b/host/frontend/gcastv2/webrtc/assets/index.html
index 69995fc..252c98e 100644
--- a/host/frontend/gcastv2/webrtc/assets/index.html
+++ b/host/frontend/gcastv2/webrtc/assets/index.html
@@ -7,6 +7,7 @@
 
     <body>
         <button id="receiveButton">Receive Media</button>
+        <button id="keyboardCaptureBtn">Capture Keyboard</button>
         <hr>
         <section class="noscroll">
             <div class="one" >