Engineering improvements and aligning with FSharp.Json.New

[dsyme]

@vsapronov - I know it's been a while since you worked on this library. I'm taking a look around and doing some minor improvements. Please chime in with any thoughts.

1. @AntyaDev forked this a while back at https://github.com/PragmaticFlow/FSharp.Json.New and it looks appropriate to look at converging these I merged a few basic commits here, up to where the rename happened, which included CI Merge some commits from FSharp.Json.New #71. @AntyaDev Do you think you'd like to send a PR for the remaining, but without the renaming?

2. Closing out or updating the PRs