[windows] Improved focus handling

Make sure the webview is focused on initial show if the window
is focused and make behaviour consistent with macOS

v3/examples/binding/assets/index.html

@@ -77,7 +77,7 @@
 </div>
 <div class="result" id="result">Please enter your name below 👇</div>
 <div class="input-box" id="input">
-    <input autocomplete="off" class="input" id="name" type="text"/>
+    <input autofocus autocomplete="off" class="input" id="name" type="text"/>
     <button class="btn" onclick="greet()">Greet</button>
 </div>
 <script src='bindings_main.js'></script>