Add Maniphest Task email creator to CCs

Summary: Fixes T9369.

Test Plan:

• Sent a mail with Mail.app to bugs@local.phacility.com.
• Used "View Raw Mail", copy-pasted it into mail.txt on disk.
• Ran cat mail.txt | ./scripts/mail/manage_mail.php --process-duplicates.
• Saw task get created and me get added as CC.
• Changed "To" to include another user, ran command again, saw task get created and other user get added as CC.

Reviewers: chad

Reviewed By: chad

Subscribers: Korvin

Maniphest Tasks: T9369

Differential Revision: https://secure.phabricator.com/D14086