Add link to extensions.adoc from index.adoc (#9735)
Add link to extensions.adoc from index.adoc (#9735)


rrosenblum/rubocop,tejasbubane/rubocop,rrosenblum/rubocop,maxjacobson/rubocop,tejasbubane/rubocop,bbatsov/rubocop,maxjacobson/rubocop,rrosenblum/rubocop,maxjacobson/rubocop,tejasbubane/rubocop,bbatsov/rubocop