This adds a test which fails because Splash inserts additional whitespace
at the beginning of code if the code has empty lines before it starts.

It seems that `\n` is identified as a valid token and then the same
substring (`\n`) is both inserted as whitespace and as a token.

This causes the insertion of additional whitespace at the beginning
of the code.

This would allow using a custom monospace font for highlighting.
This is especially useful if, say, the code is embedded into some sort of presentation 😊.
An assert could be added to make sure the font is monospace,
but I feel like that's not required.

If somebody wants to display their code in Comic Sans, all the more power to them