Add export of props types

### Description

Hi

I use `spectacle` in my presentation and I need to create some wrapper around `CodePane` component.
To be able to use the same interface in my wrapper I need to be able to import `CodePaneProps` type.

### Proposal

I suggest to add export of `CodePaneProps` type.

Also mb we can export props types of all components? It can be useful in some cases.