FsCodec.SystemTextJson (awaiting UnionConverter)
Adds a full implementation of the FsCodec.Newtonsoft
feature-set based on System.Text.Json
NOTE 1: depends on preview edition of System.Text.Json
v 5-preview.3
NOTE 2: UnionEncoder
has not yet been completed #43
See CHANGELOG
🙏 @ylibrach @NickDarvey for making it happen