default to UTF-8. Reading/writing binary data via the
editor and runner is currently *not* supported.

Standard input/output redirection is currently not supported. It is
also currently not supported to supply STDIN directly to the script,
the workaround is to use input files, supply the filenames on the
command line, and use Perl's magic ARGV operator "<>". Support for
redirections may be added in a future version.

The JavaScript shown below is not strictly necessary, it is also
possible to specify a "src