[RELEASE] Update readme to include link to announcement list

same as 3765 on master

README.md

@@ -16,6 +16,11 @@ Portions Copyright (c) 2012-2013 The Cryptonote developers.
 - Our [Vulnerability Response Process](https://github.com/monero-project/meta/blob/master/VULNERABILITY_RESPONSE_PROCESS.md) encourages responsible disclosure
 - We are also available via [HackerOne](https://hackerone.com/monero)
 
+
+## Announcements
+
+You can subscribe to an [announcement listserv](https://lists.getmonero.org) to get critical announcements from the Monero core team. The announcement list can be very helpful for knowing when software updates are needed.
+
 ## Build
 
 | Operating System      | Processor | Status |