Split content on CRLF or LF

[rlopzc]

Changes proposed in this pull request

Some emails from newsletters don't comply strictly with the RFC2822. One example is Substack. Substack emails only have LF endings.

This PR allows splitting lines by CRLF or LF.

[bcardarella]

@andrewtimberlake are you OK with this getting merged?

[andrewtimberlake]

I have just checked some of the substack emails I receive and they appear to be CRLF.
The CRLF line ending is so fundamental to email that I’m inclined not to accept this.
Both Mail.parse/2 and Mail.Parsers.RFC2822.parse/1 accept a list of lines, so it is possible to always pre-parse the lines before using them if you find yourself in a unique situation like this one.

[rlopzc]

Oh that's right, I mistakenly copied the email and my OS changed the CRLF into LF. Just checked the raw value and you are correct @andrewtimberlake :)

[andrewtimberlake]

:-) I have made that mistake enough times.