Update MiMa to 0.8.1

Author: sideeffffect

project/plugins.sbt

@@ -7,4 +7,4 @@ addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject" % "0.6.0")
 addSbtPlugin("org.scala-native" % "sbt-scala-native" % "0.4.0")
 addSbtPlugin("org.portable-scala" % "sbt-scala-native-crossproject" % "1.0.0")
 
-addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "0.3.0")
+addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "0.8.1")