docfx: Missing template file

Otherwise, <remarks> section DIV at the namespace level is always
shown, even if empty. And we do not want that now that the DIV has
a background color.

doc/docfx/default_efl/partials/namespace.tmpl.partial

@@ -0,0 +1,15 @@
+{{!Copyright (c) Microsoft. All rights reserved. Licensed under the MIT license. See LICENSE file in the project root for full license information.}}
+
+<h1 id="{{id}}" data-uid="{{uid}}" class="text-break">{{>partials/title}}</h1>
+<div class="markdown level0 summary">{{{summary}}}</div>
+<div class="markdown level0 conceptual">{{{conceptual}}}</div>
+{{#remarks}}
+<div class="markdown level0 remarks">{{{remarks}}}</div>
+{{/remarks}}
+{{#children}}
+  <h3 id="{{id}}">{{>partials/namespaceSubtitle}}</h3>
+  {{#children}}
+    <h4><xref uid="{{uid}}" altProperty="fullName" displayProperty="name"/></h4>
+    <section>{{{summary}}}</section>
+  {{/children}}
+{{/children}}