Add some release notes for v0.28.2

Summary: As per title.

Test Plan: Read it.

Reviewers: #bitcoin_abc, Mengerian

Reviewed By: #bitcoin_abc, Mengerian

Differential Revision: https://reviews.bitcoinabc.org/D14718

doc/release-notes.md

@@ -4,4 +4,9 @@ Bitcoin ABC version 0.28.2 is now available from:
 
   <https://download.bitcoinabc.org/0.28.2/>
 
-This is a maintenance release with no user-visible change.
+This is a hotfix release to patch a bug that has been introduced in the previous
+version and could cause the finalization status of an avalanche proof to be
+lost by the node under some conditions.
+
+All the nodes operators are required to update to this version before the
+November 15th 2023 eCash network upgrade.