Added Custom Headers setting description (#1480)
Added Custom Headers setting description (#1480)

* Added Custom Headers setting description

Added a description for the new __Custom Headers__ setting available in v1.1

* Clarify that it's an optional setting.

yvonnewilson/docs,yvonnewilson/docs,hamzawi06/docs,jeffreylees/docs,auth0/docs,hamzawi06/docs,yvonnewilson/docs,khorne3/docs,sandrinodimattia/docs,auth0/docs,Annyv2/docs,Catografix/docs,hamzawi06/docs,khorne3/docs,jeffreylees/docs,Catografix/docs,Catografix/docs,jeffreylees/docs,sandrinodimattia/docs,khorne3/docs,Annyv2/docs,auth0/docs,Annyv2/docs,sandrinodimattia/docs