Add synchronous signing

[gfpacheco]

Would it be too bad to add a signSync function?

In my case the JWT signing is just part of the auth configuration and I'd rather not have to make it async, that might be too hard to do on some serverless frameworks.

[panva]

It is not possible to have a non-Promise/callback based API. The module has to work in Browser and Web-like runtimes which are backed by Web Cryptography API as the crypto runtime and that is an entirely Promise-based API.

No modern runtime has an issue with supporting async/await and even top-level await is ubiquitous.

[gfpacheco]