api doc: clarify description of Stream.slice

[janriemer]

Clarify the description of 'start' and 'stop' param.

[apaleslimghost]

I'm not sure this needs documenting. The arguments work the same as [].slice.

[vqvu]

Well, they don't work exactly like Array.slice since they don't allow negative values for the stop parameter. Plus, it doesn't hurt to mention this. The MDN docs for Array.slice itself mentions the "inclusive-ness"

Zero-based index at which to end extraction. slice extracts up to but not including end.

I'll merge this since the error seems to be a spurious failure in NPM instead of something we did.