🚀: Simplify Readme and Quickstart further

[Nek-12]

Description

Based on feedback, the library is still hard to get started with. The amount of features is scary, so we can reduce this initial friction by simplifying things:

• Move the diagram into a collapsible section or into the plugin doc.
• Move the JDK configuration somewhere into "Troubleshooting" doc
• Simplify readme and avoid showcasing all of the stuff at once, or add a much simpler example on top
• Make quickstart dependency section collapsed
• Move state management / contract details into a separate state management doc?
• Explain Pipeline context typealias later, do not mention it during container generation
• Add "Complete implementation" section to the end of quickstart (optionally) to see the result