code: public static CharSink asCharSink(File file, Charset charset, FileWriteMode... modes) {
      return asByteSink(file, modes).asCharSink(charset);
    }
docs: Returns a new {@link CharSink} for writing character data to the given file using the given
  character set. The given {@code modes} control how the file is opened for writing. When no mode
  is provided, the file will be truncated before writing. When the {@link FileWriteMode#APPEND
  APPEND} mode is provided, writes will append to the end of the file without truncating it.
  
  @since 14.0