Make it possible to start the driver process in background

[AlexandreBlais42]

Klack has this snippet (https://codeberg.org/ForeverZer0/klack/src/branch/master/src/main.zig)

fn daemonize(io: Io) File {
    // Fork the process and exit the parent.
    if (std.os.linux.fork() != 0) {
        exit(0);
    }
    // Detach from terminal and start new session
    _ = std.os.linux.setsid();

    // Get handle to /dev/null to direct output to
    const dev_null = Dir.cwd().openFile(io, "/dev/null", .{
        .mode = .read_write,
    }) catch @panic("Unable to open /dev/null");

    // Redirect all input/output to /dev/null
    _ = std.os.linux.dup2(dev_null.handle, File.stdout().handle);
    _ = std.os.linux.dup2(dev_null.handle, File.stderr().handle);
    _ = std.os.linux.dup2(dev_null.handle, File.stdin().handle);

    return dev_null;
}