CompatHelper: add new compat entry for JSON at version 0.21, (keep existing compat)

Author: CompatHelper Julia

Project.toml

@@ -25,6 +25,7 @@ YAML = "ddb6d928-2868-570f-bddf-ab3f9cf99eb6"
 Base64 = "1.10.4"
 Distributed = "1.10.4"
 FilePathsBase = "0.9.21"
+JSON = "0.21"
 MPIClusterManagers = "0.2.4"
 PlatformAware = "0.6.1"
 Random = "1.10.4"