Add the <t> element and ignore whitespace outside it.

sky/tests/parser/whitespace.sky

Index: sky/tests/parser/whitespace.sky
diff --git a/sky/tests/parser/whitespace.sky b/sky/tests/parser/whitespace.sky
new file mode 100644
index 0000000000000000000000000000000000000000..8f56106a5edc586fb4df9b92b4ab72656debb538
--- /dev/null
+++ b/sky/tests/parser/whitespace.sky
@@ -0,0 +1,33 @@
+<sky>
+<import src="../resources/dump-as-markup.sky"></import>
+
+<t>
+  <span>
+    A
+    <div>
+      <span></span>
+
+          <!-- All whitespace in a subtree should be kept under <t>. -->
+
+
+      <span></span>
+    </div>
+  </span>
+
+
+  <!-- This whitespace should be preserved. -->
+
+  <span>B</span>
+</t>
+
+<div>
+  <span>
+    A
+  </span>
+
+  <!-- This whitespace should be ignored. -->
+
+  <span>B</span>
+</div>
+
+</sky>