Update template.hbs (ember-learn#369)

adding aria-label to search for accessibility purposes.

Author: MelSumner

addon/components/docs-header/search-box/template.hbs

@@ -14,5 +14,6 @@
     placeholder='SEARCH'
     class='docs-w-24 docs-text-xxs docs-p-2 docs-pl-6 docs-rounded focus:docs-bg-grey-lighter outline-none'
     data-search-box-input
-    data-test-search-box-input>
+    data-test-search-box-input
+    aria-label="search">
 </div>