Set a panic hook if use_std

[AlexKnauth]

As suggested by @CryZe in the Speedrun Tool Develop discord for improving error messages in the ASR debugger when it's using std.

When use_std is false, the start of main looks like

async fn main() {
    // TODO: Set up some general state and settings.

with no blank line between the { brace and the TODO comment.

And when use_std is true, the start of main looks like

async fn main() {
    std::panic::set_hook(Box::new(|panic_info| {
        asr::print_message(&panic_info.to_string());
    }));

    // TODO: Set up some general state and settings.

with a blank line between the set_hook call and the TODO comment.