fix line ending for windows systems in board initialisation

[dev3139]

Exploding the initial board string with PHP_EOL fails on windows systems because of the file's line separator

[brendt]

That's strange, the goal of PHP_EOL is exactly to be cross-platform compatible:

PHP_EOL (string) The correct 'End Of Line' symbol for this platform.

https://www.php.net/manual/en/reserved.constants.php

\n would only work on Linux. Maybe there's another issue at play? Unfortunately I cannot test on Windows 🤔