Merge pull request #14130 from seamuslee001/5.12

Update release notes

release-notes/5.12.4.md

 # CiviCRM 5.12.4
 
-Released April 20, 2019
+Released April 25, 2019
 
 - **[Synopsis](#synopsis)**
 - **[Bugs resolved](#bugs)**
@@ -21,14 +21,16 @@ Released April 20, 2019
 
 ## <a name="bugs"></a>Bugs resolved
 
-- **Fix mailing preview fails when viewUrl token present and mailing hash enabled." ([dev/core#891](https://lab.civicrm.org/dev/core/issues/891): [14092](https://github.com/civicrm/civicrm-core/pull/14124))**
+- **CiviMail - Fix "Preview" action when using `viewUrl` tokens and mailing hashes. ([dev/core#891](https://lab.civicrm.org/dev/core/issues/891): [14124](https://github.com/civicrm/civicrm-core/pull/14124))**
+
+- **Installer - Fix diagnostic for MySQL `utf8mb4` support. ([dev/core#880](https://lab.civicrm.org/dev/core/issues/880): [14129](https://github.com/civicrm/civicrm-core/pull/14129))**
 
 ## <a name="credits"></a>Credits
 
 This release was developed by the following authors and reviewers:
 
 Wikimedia Foundation - Eileen McNaughton; Australian Greens - Seamus Lee;
-Lighthouse Design and Consulting - Brian Shaughnessy;
+Lighthouse Design and Consulting - Brian Shaughnessy; Electronic Frontier Foundation - Mark Burdett
 
 ## <a name="feedback"></a>Feedback