isPlainObject() to support objects from another window (#1584 by @ConneXNL)
isPlainObject() to support objects from another window (#1584 by @ConneXNL)

[skip ci]
mweststrate/mobx-state-tree,mweststrate/mobx-state-tree,mobxjs/mobx-state-tree,mobxjs/mobx-state-tree,mobxjs/mobx-state-tree,mobxjs/mobx-state-tree