Add a basic sky-element custom element

sky/examples/example-element/example-element.sky

Index: sky/examples/example-element/example-element.sky
diff --git a/sky/examples/example-element/example-element.sky b/sky/examples/example-element/example-element.sky
new file mode 100644
index 0000000000000000000000000000000000000000..5382c55b0b808a65ff010a9eea3f1f559519d5d3
--- /dev/null
+++ b/sky/examples/example-element/example-element.sky
@@ -0,0 +1,25 @@
+<!--
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+-->
+<import src="/sky/framework/sky-element.sky" />
+<sky-element>
+<template>
+  <style>
+    div {
+      height: 50px;
+      width: 50px;
+      background-color: green;
+    }
+  </style>
+  <div>Hi</div>
+</template>
+<script>
+@tagname('example')
+class ExampleElement extends SkyElement {

[ojan, 2015/02/21 00:19:16]

Not directly related to this patch, but how hard would it be to have the tag
name be the class name? IMO, we should consider the implications of that.
Obviously that shouldn't block this patch though. 

[abarth-chromium, 2015/02/21 00:25:57]

Very easy.  In fact, it would be less code than we have currently.

+}
+
+_init(script) => register(script, ExampleElement);
+</script>
+</sky-element>