Add headings to troubleshoot build failures

Author: aneta-petrova

Diff for: guides/common/modules/snip_guide-not-ready.adoc

@@ -1,4 +1,4 @@
-This guide is not ready yet.
+== This guide is not ready yet
 
 Foreman is a community project.
 The source is maintained in https://github.com/theforeman/foreman-documentation/[foreman-documentation on GitHub] where you can create https://github.com/theforeman/foreman-documentation/issues[issues] and https://github.com/theforeman/foreman-documentation/pulls[pull requests].

Diff for: guides/doc-Managing_Content/master.adoc

@@ -6,10 +6,14 @@ include::common/header.adoc[]
 = {ContentManagementDocTitle}
 
 ifdef::foreman-deb[]
+== Katello plugin required
+
 The Katello plugin required to manage content in Foreman is not supported on Debian/Ubuntu.
 endif::[]
 
 ifdef::foreman-el,foreman-deb[]
+== Katello plugin required
+
 If you want to manage content using Foreman/Katello, you have to run Foreman/Katello on {EL}.
 Converting an existing Foreman installation on {EL} to Foreman/Katello is not supported.
 For more information, see {BaseURL}Installing_Server/index-katello.html[Installing Foreman Server with Katello plugin on {EL}].