Update cats-core to 2.0.0-RC1

Author: xuwei-k

build.sbt

@@ -16,7 +16,7 @@ val pbdirect = crossProject(JSPlatform, JVMPlatform)
     crossScalaVersions := Seq("2.11.12", "2.12.8", "2.13.0"),
     libraryDependencies ++= Seq(
       "com.chuusai"       %%% "shapeless"  % "2.3.3",
-      "org.typelevel"     %%% "cats-core"  % "2.0.0-M4",
+      "org.typelevel"     %%% "cats-core"  % "2.0.0-RC1",
       "org.scalatest"     %%% "scalatest"  % "3.0.8" % Test
     ),
     resolvers += "Sonatype OSS Snapshots" at