BigInt support

[4kimov]

Right now max value is Number.MAX_SAFE_INTEGER, with no support for bigints. This is an issue for tracking this feature. Hashids has support for it here (for reference): https://github.com/niieani/hashids.js/blob/master/src/hashids.ts

Todos:

• Support in encode()/decode()
• Adjust maxValue()
• Add tests specifically for bigints
• Add an example of how to use bigints

[phillipb]

+1 this is useful if you need to do something like convert a uuid to a sqid

[nathanclevenger]

+1 also required for Mongo Object IDs

[DaleLJefferson]

It would be great to revisit this now, bigint is available in all environments.

[bilogic]

Will this be a thing soon?

[mdhthahmd]

PR #39 adds opt-in BigInt support for encode() and decode(), including unsigned 64-bit values, input validation, TypeScript types, tests, and a usage example. Feedback and reviews are welcome! @4kimov