Added the software version to the mail default template and cli help … …text, updated README and build script

Updated to go 1.22.2 

Improved performance by manually handling mail server communication i… …nstead of using smtp.SendMail() and thus opening a new connection for each mail

Fixed a bug where all 1000 last notices where recognized as 'new'. Th… …is was caused by ApiEndpoint.getNotices() returning time.Time{} and a nil error in some cases.

Updated .gitignore