UPGRADE_GUIDE.md

Upgrade guide

v3 -> next

Option.from can no longer return null as a Some.

v2 -> v3

Option.from can no longer return undefined as a Some.

Option.from predicate now defaults to Predicate.ANY where it previously was Predicate.THRUTHY.

v1 -> v2

Replace all new None() with None.

The exported Noneis now a singleton.