std.mem.span used on strings that may be null?

[kaizoplant]

In the bindings, std.mem.span is used on functions that may be null for non-program ruining reasons, which ends up crashing the program without any way to intervene? In my case it was rl.getClipboardText (in this case when the clipboard is empty this happens (at least using wl-clipboard)), I'm not familiar enough with raylib to know all the other functions that would also have something like this, but there might be others? This is similar to #118, I do think in this case, just returning an optional is reasonable, although I'm not exactly sure how you'd want to go about it for auto-generated bindings.