Docs: Add journalist setup checklist
Docs: Add journalist setup checklist

This checklist contains the main points that an administrator
should run through with each journalist to verify their devices
are working properly and that a journalist has their credentials
saved.

conorsch/securedrop,heartsucker/securedrop,heartsucker/securedrop,micahflee/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,micahflee/securedrop,conorsch/securedrop,ehartsuyker/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,garrettr/securedrop,garrettr/securedrop,conorsch/securedrop,ehartsuyker/securedrop,ehartsuyker/securedrop,garrettr/securedrop,conorsch/securedrop,conorsch/securedrop,garrettr/securedrop,heartsucker/securedrop,micahflee/securedrop,micahflee/securedrop,ehartsuyker/securedrop