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