add landing page core concept file in partials

Author: rakeshAlgo

src/partials/body-landing-core-concept.hbs

@@ -0,0 +1,8 @@
+<div class="body container">
+  <main class="article" data-ceiling="topbar">
+    <article class="doc landing-page-doc">
+          {{{page.contents}}}
+
+    </article>
+  </main>
+</div>