add boilerplate methods for case class Format

[xuwei-k]

sbt/contraband support auto generate sjsonnew Formats, it's useful. but I want to convenient methods like this. because there are times when I don't want to use contraband.

The API almost same as argonaut.CodecJsons, asProductN in sbinary, and my library(play-json-extras)

Here is generated CaseClassFormats.scala

related https://github.com/eed3si9n/sjson-new/issues/12

• https://github.com/sbt/contraband/blob/v0.3.0-M5/docs/03-json.md
• https://static.javadoc.io/io.argonaut/argonaut_2.12/6.2/argonaut/CodecJsons.html
• https://github.com/argonaut-io/argonaut/blob/v6.2/project/Boilerplate.scala
• https://github.com/sbt/sbinary/blob/v0.4.4/core/src/generic.scala#L111-L134
• https://github.com/xuwei-k/play-json-extra
• http://d.hatena.ne.jp/xuwei/20140402/1396408213