Vampiro

Results 2 issues of Vampiro

The layout model's json is a very large object with many well defined attributes that could benefit from being exported as TypeScript types so that downstream devs can take advantage...

### Describe the bug The return type for [Model.getNodeById](https://github.com/caplin/FlexLayout/blob/fe0c237a792b22bbd95597a6f0dc88f4200c67ea/src/model/Model.ts#L246) is showing as `Node` when it could possibly be `undefined` due to no node with the given `id` existing. It should...