Draft release notes for 0.5.0 (#430)

Author: jni

docs/_toc.yml

@@ -180,6 +180,7 @@ subtrees:
       - file: release/index
         subtrees:
         - entries:
+          - file: release/release_0_5_0
           - file: release/release_0_4_19
           - file: release/release_0_4_18
           - file: release/release_0_4_17