Move xmailer to pascal-libs

Author: Al-Muhandis

plugins/xmailer/3rdparty/README.md

@@ -2,4 +2,7 @@
 
 This plugin offers a really simple way to send e-mails using Free Pascal.
 For those who like the procedural style, X-Mailer has the SendMail procedure. With one single line, you can configure SMTP settings and fill all the required fields as: From, To, CC, Subject and Message.
-For those who prefer an Object Oriented style, X-Mailer has the TSendMail class with the same above mentioned characteristics.
+For those who prefer an Object Oriented style, X-Mailer has the TSendMail class with the same above mentioned characteristics.
+
+*Warning*: the package has been moved to new [address](https://github.com/pascal-libs/xmailer)
+_Reason: the package works independently of brookfreepascal and can be used as a separate library_