Add PTO Ninja `taking time off` reminder subscription functionality to Paid...

Merged Darren Murph requested to merge dmurph-master-patch-01669 into master

Why is this change being made?

Add PTO Ninja taking time off reminder subscription functionality to Paid Time Off handbook section

For added context, see this issue: Slack or PTO Ninja reminder/nudge to take time off from work

Does this MR meet the acceptance criteria?

Yes

Conformity