add scala 3.0.0 to crossScalaVersions (#148)

Author: tsuyoshizawa

build.sbt

@@ -12,7 +12,7 @@ lazy val scalaOAuth2ProviderSettings =
     Seq(
       organization := "com.nulab-inc",
       scalaVersion := "3.0.0",
-      crossScalaVersions := Seq("2.13.4", "2.12.12", "2.11.12"),
+      crossScalaVersions := Seq("3.0.0", "2.13.6", "2.12.13", "2.11.12"),
       scalacOptions ++= Seq("-deprecation", "-unchecked", "-feature"),
       scalacOptions ++= unusedWarnings,
       publishTo := {