lazy val seems to be evaluated eagerly

[valydia]

When I try to generate the doc for the following sample:

```scala mdoc
lazy val valueOpt: Option[Int] = ???
```

I get the following error:

an implementation is missing
lazy val valueOpt: Option[Int] = ???
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
scala.NotImplementedError: an implementation is missing
        at scala.Predef$.$qmark$qmark$qmark(Predef.scala:288)
...

I would expect this to compile as it works with tut see this file (line 237).

[olafurpg]

Thank you for reporting! It's correct that lazy vals are currently eagerly evaluated. We can change the instrumentation to not evaluate lazy vals by changing the code somewhere around here

mdoc/mdoc/src/main/scala/mdoc/internal/markdown/Instrumenter.scala

Lines 58 to 60 in 364ebde

	private def printBinder(name: String, pos: Position): Unit = {
	sb.print(s"; $$doc.binder($name, ${position(pos)})")
	}

A pull request making the behavior consistent with tut would be welcome!