Add subsystem maintainers for Claro

Yay! Sounds amazing.

We would need confirmation from each person that they agree and understand the role as explained in https://www.drupal.org/contribute/core/maintainers#subsystem :)

Then we need a patch.

+1 to this! I understand the role and I'm happy to continue helping here.

+1 I understand the role and I'm looking forward to what we're doing next with Claro ;-)

+1 I'm happy to do it and I understand the role.

Yay! As per https://www.drupal.org/contribute/core/maintainers#decisions point 11:

If the change involves adding a new subsystem maintainer, a product, framework, or release manager must approve or refuse it (depending on the subsystem).

I believe that would be a product manager for Claro. One of the added maintainers is also a frontend framework manager, so this definitely looks like enough signoff. Ready to commit.

Committed 89cec3e and pushed to 9.2.x and 9.1.x. Thanks all for your dedication!

Additionally, Lauri added Sascha to the core maintainers list here, this allows to assign issues to others for example. I added Ben and Sascha to be maintainers of https://www.drupal.org/about/core similar to other maintainers. Also added Ben and Sascha as maintainers of https://groups.drupal.org/core, which is the legacy place we used to post announcements before the /about/core group existed.