Add support for multiple addresses as Reply-To value

[lpellegr]

The current implementation allows a single Mailbox as Reply-To value:

https://github.com/muratgozel/MIMEText/blob/master/src/MIMEMessageHeader.ts#L30

but some emails providers such as Amazon SES allow multiple.

I would be great to allow an Array of Mailbox.

[muratgozel]

It's a single mailbox as far as i remember from the standards but let me search for it. We can provide an option to allow this kind of standard violations for sure.

[lpellegr]

@muratgozel Thanks for your answer.

Based on RFC 5322, it seems Reply-To allows an address list:

https://datatracker.ietf.org/doc/html/rfc5322#section-3.6.2