[SSSD] Watch Github for next releases

[Pavel Březina]

Please note that the sssd-2.13.0 was the last release that was announced 
on sssd-devel, sssd-users and freeipa-users mailing lists.

Please, setup GitHub notifications [1] on SSSD/sssd repository [2] to 
get notified about the next releases.

Thank you,
Pavel from SSSD team.

[1] 
https://docs.github.com/en/subscriptions-and-notifications/get-started/confi...
[2] https://github.com/SSSD/sssd