[SQUIR-159] enable webhook consumer docs

[emoulson]

Description

Updates 6.0 documentation to explicitly show how to enable the webhook consumer, since its syntax is slightly different from normal job consumers.

This also adds a note that explains that the webhook consumer is required to be running for the Events API to work.

Definition Of Done

Q	A
Technical Review and 2 GTM	Todo
English Review and 1 GTM	Todo

Todo: Pending / Work in progress OK: Done / Validated -: Not needed