thunderbird: add module

Add a new Thunderbird module that uses the configuration in
`accounts.email.accounts` to setup SMTP and IMAP accounts.

Multiple profiles are not supported at this point.

modules/misc/news.nix

@@ -815,6 +815,14 @@ in
           A new module is available: 'xfconf'.
         '';
       }
+
+      {
+        time = "2022-11-04T14:56:46+00:00";
+        condition = hostPlatform.isLinux;
+        message = ''
+          A new module is available: 'programs.thunderbird';
+        '';
+      }
     ];
   };
 }