message: Add header for v0.5.0 release
diff: @@ -17,7 +17,8 @@ The format of this file is based on [Keep a Changelog](http://keepachangelog.com
  The Axom project release numbers follow [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
  -## Unreleased
  +
  +## [Version 0.5.0] - Release date 2021-05-xx
  ### Added
  - Added the MFEMSidreDataCollection class for HDF5-format simulation data collection. This
  