add link in email template for the acceptable use policy

[dmvancura]

as a user, who is newly invited to Notify through another teammate, i'd like to find policy information quickly

action:
add link to the email template that goes directly to an online copy of the Acceptable Use Policy

link would go to the Acceptable Use Policy webpage (to be created). here is the pdf version on AUP

wording for sentence – If you’re new to Notify, you’ll be directed to login.gov to create an account. By creating an account, you agree to the Notify.gov Acceptable Use Policy

[dmvancura]

making note to actually have this as a link in the footer during the accept invitation flow

[dmvancura]

working with @jonathanbobel and @stvnrlly to get the link to the Acceptable Use Policy into the 'Join Service' email