docs: README on how to build, deploy, invoke cairo contracts (#39)

* docs: add readme for cairo contracts

* imp: add how to create an account

cairo-contracts/README.md

@@ -1,3 +1,121 @@
 <div align="center">
     <h1>Starknet-IBC Cairo Contracts</h1>
 </div>
+
+This directory contains the Cairo contracts that implement the IBC protocol for
+Starknet. Currently, the ICS-20 Token Transfer application is implemented, which
+operates alongside a custom ERC20 contract. This custom contract offers a
+flexible supply through permissioned minting and burning capabilities, unlike
+the traditional ERC20 contract with a fixed supply.
+
+You can find the preset implementations of these contracts in the
+`cairo-contracts/presets` directory. The directory includes:
+
+- `erc20.cairo` - The ERC20 mintable contract implementation.
+- `transfer.cairo` - The ICS-20 transfer contract implementation.
+
+## How to build
+
+To build the contracts, you simply need to run the following command:
+
+```bash
+cd cairo-contracts
+scarb build
+```
+
+The command will compile the contracts and output the compiled contracts as JSON
+files in the `cairo-contracts/target/dev` directory, which you can then deploy
+to Starknet.
+
+- ERC20 Mintable contract: `starknet_ibc_ERC20.contract_class.json`
+- Token Transfer contract: `starknet_ibc_transfer.contract_class.json`
+
+## How to deploy
+
+### Create Starknet account
+
+To deploy the contracts, you first need to setup a Starknet account locally. You
+can find the details in the [Starknet
+documentation](https://docs.starknet.io/quick-start/set-up-an-account/), but
+briefly you have to create a signer and an account descriptor. The signer is a
+smart contract with a private key for signing transactions, which can be created
+as follows:
+
+```bash
+# Create the default directory
+mkdir -p ~/.starkli-wallets/deployer
+
+# Generate the keystore file from a private key
+starkli signer keystore from-key ~/.starkli-wallets/deployer/keystore.json
+
+# Paste the private key of your smart wallet.
+# You can obtain the private key from your smart wallet (e.g. Braavos or ArgentX)
+Enter private key:
+
+# Enter a password of your choice.
+Enter password:
+
+# To view the details of the created keystore file.
+cat ~/.starkli-wallets/deployer/keystore.json
+```
+
+The account descriptor is a JSON file that contains the info of the signer,
+which can be created as follows:
+
+```bash
+# Generates the account descriptor file
+starkli account fetch <SMART_WALLET_ADDRESS> --output ~/.starkli-wallets/deployer/account.json
+
+# To see the details of your Account Descriptor file.
+cat ~/.starkli-wallets/deployer/account.json
+```
+
+### Setup environment
+
+Next, create an `.env` file in the root directory of the project. You can use
+the `.env.example` file as a template, which contains the following content:
+
+```bash
+ERC20_CONTRACT_SRC=${CONTRACT_SRC:-$(pwd)/cairo-contracts/target/dev/starknet_ibc_ERC20Mintable.contract_class.json}
+ICS20_CONTRACT_SRC=${CONTRACT_SRC:-$(pwd)/cairo-contracts/target/dev/starknet_ibc_Transfer.contract_class.json}
+RPC_URL=https://starknet-sepolia.public.blastapi.io/rpc/v0_7
+ACCOUNT_SRC="${HOME}/.starkli-wallets/deployer/account.json"
+KEYSTORE_SRC="${HOME}/.starkli-wallets/deployer/keystore.json"
+KEYSTORE_PASS=<KEYSTORE_PASSWORD>
+ERC20_CLASS_HASH=""
+ICS20_CLASS_HASH=""
+CONTRACT_ADDRESS=""
+```
+
+Make sure to replace `<KEYSTORE_PASSWORD>` with the password of your Starknet
+account.
+
+If you have previously declared the contracts on-chain, you can fill in the
+`ERC20_CLASS_HASH` and `ICS20_CLASS_HASH` fields to use that particular versions
+for deploying the contracts. Otherwise, the script will declare the contracts as
+well.
+
+### Deploy contracts
+
+Now that you have set up the environment, you can deploy the contracts by
+running the following command:
+
+```bash
+./scripts/deploy.sh
+```
+
+The script will deploy a single instance of the ICS20 contract to the Starknet
+network and return the contract address.
+
+## How to invoke
+
+To interact with the deployed contracts, you can run the following command:
+
+```bash
+./scripts/invoke.sh
+```
+
+Currently, the script only invokes the `ibc_token_transfer` interface to confirm
+that the contract is working as expected. To interact with other interfaces,
+which require passing more complex and lengthy arguments, it is recommended to
+use the client-side Rust or Typescript implementation.