Add "landing-page-doc" to class list for capella

This will ensure the formatting of e.g. h1 is consistent.

Author: osfameron

src/partials/body-landing-page-capella.hbs

@@ -11,7 +11,7 @@
 {{/with}}
 {{/if}}
 <main class="capella-article" data-ceiling="topbar">
-<article class="doc landing-page-capella">
+<article class="doc landing-page-doc landing-page-capella">
 <img class="opening-image" src="{{{uiRootPath}}}/img/stars.svg" />
 
 {{{page.contents}}}