use named exports

[gurgunday]

Closes #253

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[Uzlopak]

Why did you remove the signer exports?

[gurgunday]

Because they were created for destructuring purposes but named exports are defaulted to when they can't be found

const { sign } = require("./plugin");
const { fastifyCookie } = require("./plugin");
const fastifyCookie2 = require("./plugin");

console.log(sign); // [Function: sign]
console.log(fastifyCookie.sign); // [Function: sign]
console.log(fastifyCookie2.sign); // [Function: sign]

[Uzlopak]

Ok. Too much circularity :D

[mcollina]

lgtm

[gajus]

Thank you