[TASK] Write Batched Reward Tree Processing documentation

[akileshtangella]

https://www.notion.so/hicommonwealth/Batched-Reward-Tree-Processing-7d51b34188584288af9266e7f2a06542?pvs=4

Expand on following topics:

• [ ] What is batched reward tree processing?
• [ ] What role does a relayer play?
• [ ] What data is sent to the relayer if at all? What data does the relayer listen to?
• [ ] What are the fees / incentives? (Are there any? Do we have ideas, add remarks)
• [ ] How is privacy / security preserved? Can the relayer tamper with deposits or add fake deposits?

Outline

• [ ] Overview
• [ ] Lifecycle (where is data moving, what is being communicated, etc.)
• [ ] Implementation Details (smart contract calls, event watching, etc.)
• [ ] Fees and Incentives
• [ ] Privacy and Security
• [ ] Links (code links, repo links, etc.)