Documentation not updated to add the possibility of setting cookie secure

[kaush1889]

Issue in ./help/introduction.md

The documentation says that we cannot set the s_cc and mbox cookies as secure but that is old information as now the configurations are available. For example, for mbox there is a way described in below article:

https://developer.adobe.com/target/implement/client-side/atjs/atjs-functions/targetglobalsettings/?lang=en