feature: add blank line in enums between constants & declarations

[clementdessoude]

Fix #309

In this PR, I always add a blank line before enumBodyDeclarations.

So we would get this formatting

// This input
public enum EnumWithExtraCommaAndEnumBodyDeclarations {
  THIS_IS_GOOD("abc"),
  THIS_IS_FINE("abc");
  public static final String thisWillBeDeleted = "DELETED";
}

// or this input
public enum EnumWithExtraCommaAndEnumBodyDeclarations {
  THIS_IS_GOOD("abc"),
  THIS_IS_FINE("abc");
  public static final String thisWillBeDeleted = "DELETED";
}

// will be formatted to this output
public enum EnumWithExtraCommaAndEnumBodyDeclarations {
  THIS_IS_GOOD("abc"),
  THIS_IS_FINE("abc");

  public static final String thisWillBeDeleted = "DELETED";
}