docs(l2): add quick handsOn on bridging assets between L1 and L2 (#2589)

**Motivation**

This PR tries to show some basic walkthrough on moving assets between
the two chains in the docs

**Description**

* Add an example of how to deposit and how to withdraw funds in L2 and
L1.
* Explain the deposit functions from the CommonBridge contract in the L1

Closes #2524

---------

Co-authored-by: Ivan Litteri <[email protected]>
Co-authored-by: Javier Rodríguez Chatruc <[email protected]>

Author: 3 people

crates/l2/docs/README.md

@@ -37,6 +37,83 @@ Make sure docker is running!
 
 For more information on how to run the L2 node with the prover attached to it, the [Prover Docs](./prover.md) provides more insight.
 
+## Bridge Assets
+
+### Funding an L2 Account from L1
+
+To transfer ETH from Ethereum L1 to your L2 account:
+
+1. Prerequisites:
+   - An L1 account with sufficient ETH balance, for developing purpose you can use:
+      - Address: `0x8943545177806ed17b9f23f0a21ee5948ecaa776`
+      - Private Key: `0xbcdf20249abf0ed6d944c0288fad489e33f66b3960d9e6229c1cd214ed3bbe31`
+   - The address of the deployed CommonBridge contract. 
+   - An Ethereum utility tool like [Rex](https://github.com/lambdaclass/rex)
+
+2. Make a deposit:
+
+   Using Rex is as simple as:
+   ```Shell
+   # Format: rex l2 deposit <AMOUNT> <PRIVATE_KEY> <BRIDGE_ADDRESS> [L2_RPC_URL]
+   rex l2 deposit 50000000 0xbcdf20249abf0ed6d944c0288fad489e33f66b3960d9e6229c1cd214ed3bbe31 0x65dd6dc5df74b7e08e92c910122f91d7b2d5184f
+   ```
+
+3. Verification:
+
+   Once the deposit is made you can verify the balance has increase with:
+   ```Shell
+   # Format: rex l2 balance <Address> [RPC_URL]
+   rex l2 balance 0x8943545177806ed17b9f23f0a21ee5948ecaa776
+   ```
+
+For more information on what you can do with the CommonBridge see [here](./contracts.md).
+
+### Withdrawing funds from the L2 to L1
+
+1. Prerequisites:
+   - An L2 account with sufficient ETH balance, for developing purpose you can use:
+      - Address: `0x8943545177806ed17b9f23f0a21ee5948ecaa776`
+      - Private Key: `0xbcdf20249abf0ed6d944c0288fad489e33f66b3960d9e6229c1cd214ed3bbe31`
+   - The address of the deployed CommonBridge L2 contract (note here that we are calling the L2 contract instead of the L1 as in the deposit case). You can use:
+      - CommonBridge L2: `0x000000000000000000000000000000000000ffff`
+   - An Ethereum utility tool like [Rex](https://github.com/lambdaclass/rex).
+
+2. Make the Withdraw:
+
+    Using Rex we simply use the `rex l2 withdraw` command (it uses the default CommonBridge address).
+    ```Shell
+    # Format: rex l2 withdraw <AMOUNT> <PRIVATE_KEY> [RPC_URL]
+    rex l2 withdraw 5000 0xbcdf20249abf0ed6d944c0288fad489e33f66b3960d9e6229c1cd214ed3bbe31
+    ```
+
+    If the withdraw is successful, the hash will be printed in the format:
+
+    ```
+    Withdrawal sent: <L2_WITHDRAWAL_TX_HASH>
+    ...
+    ```
+
+3. Claim the Withdraw:
+
+   After making the withdraw it has to be claimed in the L1. This is done with the L1 CommonBridge contract. We can use the Rex command `rex l2 claim-withdraw`. Here we have to use the tx hash obtained in the previous step. Also, it is necessary to wait for the block that includes the withdraw to be verified.
+
+   ```Shell
+   # Format: rex l2 claim-withdraw <L2_WITHDRAWAL_TX_HASH> <PRIVATE_KEY> <BRIDGE_ADDRESS>
+   rex l2 claim-withdraw <L2_WITHDRAWAL_TX_HASH> 0xbcdf20249abf0ed6d944c0288fad489e33f66b3960d9e6229c1cd214ed3bbe31 0x65dd6dc5df74b7e08e92c910122f91d7b2d5184f
+   ```
+
+4. Verification:
+
+   Once the withdrawal is made you can verify the balance has decrease with:
+   ```Shell
+   rex l2 balance 0x8943545177806ed17b9f23f0a21ee5948ecaa776
+   ```
+
+   And also increased in the L1:
+   ```Shell
+   rex balance 0x8943545177806ed17b9f23f0a21ee5948ecaa776
+   ```
+
 ## Configuration
 
 Configuration consists of two steps, the parsing of a `.toml` config file and the creation and modification of a `.env` file, then each component reads the `.env` to load the environment variables. A detailed list is available in each part documentation.

crates/l2/docs/contracts.md

@@ -17,6 +17,32 @@
 
 Allows L1<->L2 communication from L1. It both sends messages from L1 to L2 and receives messages from L2.
 
+#### Deposit Functions
+
+##### Simple Deposits
+
+- Send ETH directly to the contract address using a standard transfer
+- The contract's `receive()` function automatically forwards funds to your identical address on L2
+- No additional parameters needed
+
+##### Deposits with Contract Interaction
+
+```solidity
+function deposit(DepositValues calldata depositValues) public payable
+```
+
+Parameters:
+
+- `to`: Target address on L2
+- `recipient`: Address that will receive the ETH on L2 (can differ from sender)
+- `gasLimit`: Maximum gas for L2 execution
+- `data`: Calldata to execute on the target L2 contract
+
+This method enables atomic operations like:
+
+- Depositing ETH while simultaneously interacting with L2 contracts
+- Funding another user's L2 account
+
 ### `OnChainOperator`
 
 Ensures the advancement of the L2. It is used by the operator to commit batches of blocks and verify batch proofs.