Add doobie-postgres-tethys integration

[Roman-Statsura]

How do you feel about adding a new module with Put and Get instances for json and jsonb for tethys similar to doobie-postgres-circe?

smth like that

trait JsonBTethysInstances {

  implicit private val showPGobject: Show[PGobject] = Show.show(_.getValue.take(250))

  def jsonbPut[T: JsonWriter]: Put[T] =
    Put.Advanced.other[PGobject](
      NonEmptyList.of("jsonb")
    ).tcontramap { a =>
      val o = new PGobject
      o.setType("jsonb")
      o.setValue(a.asJson)
      o
    }

  def jsonbGet[T: JsonReader]: Get[T] =
    Get.Advanced.other[PGobject](
      NonEmptyList.of("jsonb")
    ).temap(_.getValue.jsonAs[T].leftMap(_.getMessage))
}

and the similar for "json"

[jatcwang]

Thanks for the idea! I haven't heard of tethys before but happy to add the module since the code footprint should be small.
No guarantee that it stays in-tree though (mainly if it causes significant maintenance burden).