Add instructions for previewing articles

I am not sure if this is "the" way to do this, bit it is "a" way.

Change-Id: I42f661356485cf041a7245393d6def19e46f7159
Reviewed-on: https://gerrit.causes.com/26307
Reviewed-by: Greg Hurrell <greg@causes.com>
Tested-by: Greg Hurrell <greg@causes.com>