Handbook: Security -> Doas

Add an actual headline for the small chapter.

documentation/content/en/books/handbook/security/_index.adoc

@@ -2127,6 +2127,8 @@ While sessions are logged, any administrator is able to remove sessions and leav
 The `sudoreplay` is extremely extendable. Consult the documentation for more information.
 
 [[security-doas]]
+== Using doas as an alternative to sudo
+
 As an alternative to package:security/sudo[] package:security/doas[] can be used to provide the ability for users to get enhanced privileges.
 
 The doas utility is available via the ports collection in package:security/doas[] or via the man:pkg[8] utility.