Work with larger indices

[make-github-pseudonymous-again]

import * as natural from '@aureooms/js-natural' ;
import * as integer from '@aureooms/js-integer' ;
import { sequences } from '@aureooms/js-integer-sequences' ;

const seq = sequences( natural , integer ) ; // lazy
const F = seq.Fibonacci ; // class getter, build object if not already build
const x = F.nth( "82973927982373928739278937929382783927" ) ;