Support trailing commas in sbt files

[olafurpg]

Currently, the sbt dialect is based of 211, which does not permit trailing commas. We should base it off the default lenient dialect.

[dwijnand]

I'm happy to try and fix this. How do I setup a failing test for this? I'm happy to look at prior art/PRs.

[olafurpg]

Very cool @dwijnand See

• scalafmt/scalafmt-core/shared/src/main/scala/org/scalafmt/config/ScalafmtRunner.scala

  Line 92 in 509bad6

  val sbt = default.copy(dialect = scala.meta.dialects.Sbt0137)

• https://github.com/scalameta/scalameta/blob/ecdaadfba7e883a93f4ddf2be7120631975a86ed/scalameta/dialects/shared/src/main/scala/scala/meta/dialects/package.scala#L173-L174

As for failing test, I think it should be sufficient to have a org.scalafmt.DialectSuite FunSuite that unit tests that

ScalafmtRunner.sbt("""
lazy 
val x = project(
  a,


  b,
)
"".parse[Source].get

doesn't crash