ISBAT Implementing ability to select a custom post type instead of regular posts in Posts block

### Is your feature request related to a problem? Please describe.
No, I want to see if other custom post types can be used by Posts block in one of the latest updates

### Describe the solution you'd like
Usage of the Posts block by a custom post type, ideally a selection box where you could select a custom post instead of a regular post type

### Describe alternatives you've considered
The only alternative would be picking a dedicated category which is not always applicable

### Additional context/screenshots
If there is a technical way of implementing this functionality, it should be at least considered

The selection box may be placed here for an example: https://i.imgur.com/t9estaH.png