feat: 🚀 Add a ScalaDsl

[gaeljw]

Closes #123

I didn't implement the ideal DSL that I had in mind in the original issue but this is a first step which I believe is already nice to use.

// Pact JVM LambdaDsl
val dsl: DslPart = LambdaDsl
  .newJsonBody { rootObj =>
    rootObj.`object`(
      "keyA",
      o => {
        o.stringType("a1")
        o.stringType("a2")
        ()
      }
    )
    rootObj.array(
      "keyB",
      a => {
        a.integerType()
        ()
      }
    )
    ()
  }
  .build()

// Pact4s ScalaDsl
val dsl: DslPart = newJsonObject { rootObj =>
  rootObj.newObject("keyA") { o =>
    o.stringType("a1")
    o.stringType("a2")
  }
  rootObj.newArray("keyB") { a =>
    a.integerType()
  }
}

If we would like to go further, we'd need to duplicate every DSL method from Pact JVM which sounds painful in the long term. Note for future readers, in Scala 3 this would be slightly simpler thanks to Context Functions (https://dotty.epfl.ch/docs/reference/contextual/context-functions.html#example-builder-pattern).

[gaeljw]

Any feedback is welcome @jbwheatley :)

[jbwheatley]

Hey Gael, thanks for this, looks good. Would you mind formatting the implicit classes so they are aligned with how they are done elsewhere in the project?

i.e.

object Foo {
  implicit class FooOps(val f: String) extends AnyVal {}
}

trait Foo {
  implicit def toFooOps(f: String): FooOps = new FooOps(f)
}

[gaeljw]

@jbwheatley Done :)