Are components valid selectors?

[timswalling]

Firstly, thank you to all the maintainers and contributors who have worked on this - this package makes testing Preact apps so much easier!

I was just wondering if there's there any reason why a component can't be used as a selector for the render context's find method? (find(Selector) or find(ImportedComponent), for example.)

The documentation and types added in #78 only cover nodes, but as far as I can tell this already works: selToWhere(Selector) returns { nodeName: Selector }, and isWhere already handles nodeName values that are functions.

This would make testing in TypeScript easier, as creating a JSX selector without the required props causes type errors, while including the required props can make the test overly specific.

Happy to open a PR to add tests and update the types if that's all that's required.