RSS/Atom feeds have a lot of noise

### Description

The current RSS/Atom feeds contain a lot of noise. For example, `construct-hub-probe` which holds no value outside of the construct hub.

### Use Case

The RSS/Atom feeds are great to keep an eye on newly created constructs, but seeing so much noise of both AWS-CDKv1 constructs and construct-hub-probe makes it harder to see what's new.

I propose a second RSS/Atom feed which only shows 3rd party constructs, those not directly part of the AWS CDK, cdk8s, and other 'core' construct APIs.

### Other information

_No response_