lib: give names to promisified `exists()` and `question()`

import { promisify } from 'node:util';
import fs from 'node:fs';
import readline from 'node:readline';
[
        fs.exists,
        readline.createInterface({input:process.stdin}).question,
].forEach(fn=>console.log(promisify(fn).name));

Old:

value
# empty string

New:

exists
question