Parts of askBool-generated questions can be unreadable

[koachan]

I noticed that parts of questions made by zinput can be unreadable when used with dark/light-themed terminal. Sample program and its output:

const zinput = @import("zinput");

pub fn main() void {
    _ = zinput.askBool("The question is unreadable on light theme, and the y/n prompt is unreadable on dark theme") catch return;
}

[koachan]

I see that the library uses some hardcoded color values, would it be okay if it's changed into a more neutral combination? If so then I'll prepare a PR for that.

https://github.com/ziglibs/zinput/blob/5e0d781eee025cfea271dd10c1939d201fe4fd25/src/main.zig#L48