add utime method

I usually use utime core function when downloading file from Web server.
Like this:

    # ...
    $dir->child($file)->spew_raw( $res->{content} );
    
    my $res = HTTP::Tiny->new->get("$url/$file");
    if ( $res->{headers}{'last-modified'} ) {
        my $dt = DateTime::Format::HTTP->parse_datetime(
            $res->{headers}{'last-modified'},
        );
        utime $dt->epoch, $dt->epoch, $dir->child($file)->canonpath;
        #$dir->child($file)->utime($atime, $mtime); <-- ?
    }
    # ...

It'll be convenient if utime is supported from Path::Tiny.
If this is not proper for Path::Tiny, please just ignore this pull-req. :-)