Fix JS code gen for Byte, Short and Char literals.

They were all erroneously translated to `IntLiteral`s.

Author: sjrd

compiler/src/dotty/tools/backend/sjs/JSCodeGen.scala

@@ -936,7 +936,13 @@ class JSCodeGen()(implicit ctx: Context) {
             js.Skip()
           case BooleanTag =>
             js.BooleanLiteral(value.booleanValue)
-          case ByteTag | ShortTag | CharTag | IntTag =>
+          case ByteTag =>
+            js.ByteLiteral(value.byteValue)
+          case ShortTag =>
+            js.ShortLiteral(value.shortValue)
+          case CharTag =>
+            js.CharLiteral(value.charValue)
+          case IntTag =>
             js.IntLiteral(value.intValue)
           case LongTag =>
             js.LongLiteral(value.longValue)