Add ability to set In-Reply-To tag (#81) * Add ability to set In-Reply-To tag This is useful to reply to a specific email, e.g. to a patch sent by email on a mailing list. Please note that both the In-Reply-To and the References tags are filled-in. In theory, only the In-Reply-To tag should be enough but they are both linked to the same idea and in theory most emails readers should support a Message-ID given in In-Reply-To tag. So just in case, we fill both to imitate many email clients. Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net> * Update test.yml Co-authored-by: Dawid Dziurla <dawidd0811@gmail.com>