website: Updated the mailing list page

Made an update to the mailing list page of the website
to add the gem5-announce mailing list,
as it was not previously listed.

Change-Id: I4295fe2efc7fa2fd4ef6c2b561b691fb51ce17c1
Jira: https://gem5.atlassian.net/browse/GEM5-459
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/28027
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: Bobby R. Bruce <bbruce@ucdavis.edu>
diff --git a/_pages/mailing_list.md b/_pages/mailing_list.md
index adf8dc0..2dc578a 100644
--- a/_pages/mailing_list.md
+++ b/_pages/mailing_list.md
@@ -4,7 +4,7 @@
 permalink: /mailing_lists/
 ---
 
-There are two mailing lists for gem5:
+There are three mailing lists for gem5:
 
 * gem5-dev ([subscribe](http://m5sim.org/mailman/listinfo/gem5-dev)) ---
 Discussions regarding gem5 development. Bug reports should be submitted to our
@@ -12,6 +12,8 @@
 list can be used to discuss bugs in greater detail.
 * gem5-users ([subscribe](http://m5sim.org/mailman/listinfo/gem5-users)) ---
 General discussions about gem5 and its use.
+* gem5-announce ([subscribe](http://m5sim.org/cgi-bin/mailman/listinfo/gem5-announce)) ---
+General gem5 annoucements. 
 
 # Mail Archive
 
@@ -23,6 +25,9 @@
 The gem5-users mail archive can be found [here](
 https://www.mail-archive.com/gem5-users@gem5.org).
 
+The gem5-announce mail archive can be found [here](
+https://www.mail-archive.com/gem5-announce@gem5.org/).
+
 # Alternative communication channels
 
 [Stack Overflow](https://stackoverflow.com) can be used to crowd-source