code: public static void copy(File from, Charset charset, Appendable to) throws IOException {
      asCharSource(from, charset).copyTo(to);
    }
docs: Copies all characters from a file to an appendable object, using the given character set.
  
  @param from the source file
  @param charset the charset used to decode the input stream; see {@link StandardCharsets} for
  helpful predefined constants
  @param to the appendable object
  @throws IOException if an I/O error occurs