[DerManoMann]

The last part of 3.0.0 before the tag. The README gets two sections:

• What is verified: response bodies only, what makes a response skipped, and what the schema validation does and does not check. Each point was checked against the code.
• Upgrading from 2.x: the requirement changes and the breaking changes from Raise the floor to PHP 8.2, and test both adapters in one matrix #77 to Raise phpstan to level 7, with no baseline #82, grouped by validation, API and adapters.

TODO goes, since its other item, the Guzzle middleware, shipped in #79.