Update readme to use 2.3.0 since it seems 2.3.0 has been released

Author: felher

README.md

@@ -17,7 +17,7 @@ Scala 2.11, Scala 2.12, Scala 2.13 and Scala 3.0.0-RC2/RC3 are supported.
 
 To get started with SBT, add one (or both) of these dependencies:
 
-- `libraryDependencies += "io.github.cquiroz" %%% "scala-java-time" % "2.2.2"`
+- `libraryDependencies += "io.github.cquiroz" %%% "scala-java-time" % "2.3.0"`
 
 #### Documentation