java.lang.ClassNotFoundException: com.oreilly.learningsparkexamples.mini.scala.WordCount

[zhanwen]

I run sbt clean package is successful. and then execute
spark-submit --class com.oreilly.learningsparkexamples.mini.scala.WordCount ./target/.. ./README.md ./wordcount
show ClassNotFoundException.
build.sbt

version := "0.0.1"   
scalaVersion := "2.10.6"   
// additional libraries   
libraryDependencies ++= Seq(   
  "org.apache.spark" %% "spark-core" % "2.2.0" % "provided"   
)    

spark version is 2.2.0

scala version is   
`Scala code runner version 2.10.6 -- Copyright 2002-2013, LAMP/EPFL`