Feature request: Add methods to check for sender and recipient(s)

[wazum]

For the upcoming feature to look for the nth message, I propose a new
feature request (will provide a PR):

• add method seeSenderInLastEmail/seeSenderInNthEmail to check for the correct sender
• add method seeRecipientInLastEmail/seeRecipientInNthEmail to check for certain recipient(s)

The data is there and could easily be integrated in the \Codeception\Util\Email entity and \Codeception\Module\MailCatcher module.

[Jamesking56]

Sounds good, looking forward to the PR 👍