add license/language for Claws Mail

README.md

@@ -450,7 +450,7 @@ Log management tools: collect, parse, visualize...
 
 **[`^        back to top        ^`](#awesome-sysadmin)**
 
-- [Claws Mail](http://www.claws-mail.org/) - Old school email client (and news reader), based on GTK+. ([Source Code](https://git.claws-mail.org/?p=claws.git;a=tree))
+- [Claws Mail](http://www.claws-mail.org/) - Old school email client (and news reader), based on GTK+. ([Source Code](https://git.claws-mail.org/?p=claws.git;a=tree)) `GPL-3.0` `C`
 - [ImapSync](http://imapsync.lamiral.info/) - Simple IMAP migration tool for copying mailboxes to other servers. ([Source Code](https://github.com/imapsync/imapsync))
 - [Mutt](http://www.mutt.org/) - Small but very powerful text-based mail client. ([Source Code](https://gitlab.com/muttmua/mutt))
 - [Sylpheed](http://sylpheed.sraoss.jp/en/) - Still developed predecessor to Claws Mail, lightweight mail client. ([Source Code](https://github.com/sylpheed-mail/sylpheed))