docs: add tldr single step prereqs note

[CyrusVorwald]

Checklist:

• [ ] I have performed a self-review of my own code
• [ ] I have documented my code in accordance with the documentation guidelines
• [ ] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have run the unit tests
• [ ] I only have one commit (if not, squash them into one commit).
• [ ] I have a descriptive commit message that adheres to the commit message guidelines

Please review the CONTRIBUTING.md file for detailed contributing guidelines.