CompatHelper: add new compat entry for "JSON" at version "0.21"

Author: github-actions[bot]

Project.toml

@@ -26,6 +26,7 @@ Distributions = "0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 1"
 DocStringExtensions = "0.8, 0.9, 0.10, 1"
 GraphPlot = "0.3.1, 0.4"
 Graphs = "0.10.2, 0.11, 1"
+JSON = "0.21"
 JSON2 = "0.3.1"
 LightGraphs = "1.2, 1.3"
 Neo4j = "2"