docs: rollup contract managment&interaction (#95)

## Description

This PR introduces one big doc for rollup bsn contract managment

Resolves #79

---------

Co-authored-by: Vitalis Salis <[email protected]>
Co-authored-by: Runchao Han <[email protected]>

Author: 3 people

CHANGELOG.md

@@ -80,6 +80,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ### Improvements
 
+* [#95](https://github.com/babylonlabs-io/rollup-bsn-contracts/pull/95) docs: rollup contract managment
 * [#83](https://github.com/babylonlabs-io/rollup-bsn-contracts/pull/83) docs: rollup bsn contract guide
 * [#84](https://github.com/babylonlabs-io/rollup-bsn-contracts/pull/84) chore: consolidate tests for InstantiateMsg
 * [#81](https://github.com/babylonlabs-io/rollup-bsn-contracts/issues/81) Add

docs/assets/interaction.png

@@ -0,0 +1,85 @@
+# Rollup BSN Contract Interaction
+
+## Table of Contents
+
+1. [Introduction](#introduction)
+2. [Committing Public Randomness](#1-committing-public-randomness)
+3. [Submitting Finality Signatures](#2-submitting-finality-signatures)
+
+## Introduction
+
+<img width="3100" height="772" alt="governance" src="./assets/interaction.png" />
+
+The Rollup BSN contract is a CosmWasm smart contract deployed on the Babylon
+Genesis chain that tracks finality signatures for rollup blocks. Interaction with
+the contract is performed by submitting messages to commit public randomness and
+to submit finality signatures for rollup blocks. All interactions require the
+submitter's BTC public key to be added to the contract's `allow-list`.
+
+Each operation is executed with:
+
+```shell
+babylond tx wasm execute <CONTRACT_ADDRESS> '$JSON_MSG'
+```
+**Note**: `<CONTRACT_ADDRESS>` refers to the address of the deployed Rollup BSN
+contract on Babylon. `$JSON_MSG` is the execute message in JSON format,
+described below.
+
+## 1. Handling Public Randomness Commitments
+
+To commit a batch of public randomness values, submit a Merkle root to the
+contract. This prevents adaptive randomness generation based on block contents.
+
+**Message Format:**
+```shell
+JSON_MSG={
+  "commit_public_randomness": {
+    "commitment": "$MERKLE_ROOT",
+    "fp_pubkey_hex": "$FP_BTC_PUBKEY",
+    "num_pub_rand": $COUNT,
+    "signature": "$SIGNATURE",
+    "start_height": $START_BLOCK
+  }
+}
+```
+
+> **Variables:**  
+> `$MERKLE_ROOT`: Hex-encoded Merkle root of the randomness batch (string)  
+> `$FP_BTC_PUBKEY`: Hex-encoded compressed BTC public key of the submitter
+> (string)  
+> `$COUNT`: Number of randomness values committed (integer)  
+> `$SIGNATURE`: Signature over the commitment (string)  
+> `$START_BLOCK`: Rollup block height for the first randomness value (integer)
+
+## 2. Submitting Finality Signatures
+
+To submit a finality signature for a rollup block, send a message that proves
+the use of previously committed randomness via a Merkle proof.
+
+**Message Format:**
+```shell
+JSON_MSG={
+  "submit_finality_signature": {
+    "block_hash": "$BLOCK_HASH",
+    "fp_pubkey_hex": "$FP_BTC_PUBKEY",
+    "height": $BLOCK_HEIGHT,
+    "proof": "$MERKLE_PROOF",
+    "pub_rand": "$PUBLIC_RANDOMNESS",
+    "signature": "$SIGNATURE",
+    "l1_block_hash_hex": "$L1_HASH",
+    "l1_block_number": $L1_NUMBER
+  }
+}
+```
+
+> **Variables:**  
+> `$BLOCK_HASH`: Hex-encoded rollup block hash (string)  
+> `$FP_BTC_PUBKEY`: Hex-encoded compressed BTC public key of the submitter
+> (string)  
+> `$BLOCK_HEIGHT`: Rollup block height (integer)  
+> `$MERKLE_PROOF`: Merkle proof that `pub_rand` is in the committed Merkle root
+> (string)  
+> `$PUBLIC_RANDOMNESS`: Revealed randomness value (string)  
+> `$SIGNATURE`: Signature over the message (string)  
+> `$L1_HASH`: (Optional) L1 block hash (string)  
+> `$L1_NUMBER`: (Optional) L1 block number (integer)