Describe report-driven approach for fixes in recepies

[rdiachenko]

Every recipe must follow Option 2: Report-Driven Recipe Execution described here #8 (comment), and fix only that code, which Checkstyle gives violations for.

We need to clearly communicate this approach for contributors to this project. Let's start by updating README with contributions notes and brief description of the approach to implement every recipe in this project.

Additionally, explore ways to enforce this approach and fail ci if implemented recipe in the PR doesn't follow it.