Proposal-index-from-end array[^n]

# Cyril Auburtin (3 months ago)

There has been many "array.last()" and similar proposals on es-discuss

One has emerged: keithamus/proposal-array-last It adds Array.prototype.lastIndex and Array.prototype.lastItem

I'd like to extend this idea with a syntax like arr[^n] (stands for arr[arr.length - n]), I wrote it in keithamus/proposal-array-last#28

The idea comes from @rbuckton tc39/proposal-slice-notation#30