It is currently impossible to know when the user presses a special key in Console Window Host (the default terminal, conhost.exe) or Windows Terminal.

Here's a test script (needs --unstable because of Deno.setRaw()):

const stdinRid = Deno.stdin.rid;
if (Deno.isatty(stdinRid))
    Deno.setRaw(stdinRid, true);

(async () => {
    for await (const data of Deno.iter(Deno.stdin)) {
        if (data[0] === 0x03) // Ctrl+C
            Deno.exit();
        console.log(data);
    }
})();

This could log an escape sequence when the user presses, for example, the arrow keys (I think it does on Linux), but it logs nothing.