isEmpty should probably be usable as type-guard against null, undefined, and Record<PropertyKey, never>

[matthew-holder-revvity]

Since isEmpty checks for the nullish values, maybe it should return a value is predicate that identifies it as one of the nullish values or the empty object type (a la how it's defined in @types/lodash). (see: https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/lodash/common/lang.d.ts at line 574)