Update installing.adoc

tutorials/forge-hol/chapters/installing.adoc

@@ -5,6 +5,8 @@
 It's very simple install Forge CLI.
 Just download the https://repository.jboss.org/nexus/service/local/artifact/maven/redirect?r=releases&g=org.jboss.forge&a=forge-distribution&v=LATEST&e=zip&c=offline[ZIP] to install Forge natively on your preferred Operation System.
 
+==== Windows 
+
 On Windows, you can do: + 
 Extract the distribution archive, to the directory you wish to install Forge. + 
 Add the FORGE_HOME environment variable.
@@ -15,6 +17,8 @@ In the same dialog, add %FORGE_HOME%\bin to the system path.
 
 image::installing/windows/forge-cli-install2.png[title="Installing Forge CLI Step 2"]
 
+==== Mac OS X or Linux
+
 On Mac OS X or Linux, you can do: + 
 Extract the distribution archive, to the directory you wish to install Forge. + 
 In a command terminal, add the FORGE_HOME environment variable, e.g: