[eth] Add token swap example application (#518)

* add swap example

* make example a swap

* whatever

* make swap

* working on this thing

* it kind of works

* whatever

* doc

* cleanup

* pre-commit

* pr comments

* fix tests

* add disclaimer

Co-authored-by: Jayant Krishnamurthy <[email protected]>

Author: jayantk

target-chains/ethereum/examples/oracle_swap/README.md

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+# Pyth Oracle AMM
+
+This directory contains an example oracle AMM application using Pyth price feeds.
+The oracle AMM manages a pool of two tokens and allows a user to trade with the pool at the current Pyth price.
+
+This application has two components. The first component is a smart contract (in the `contract` directory) that manages the pool and implements the trading functionality.
+The second is a frontend application (in the `app` directory) that communicates with the smart contract.
+
+Please see the [Pyth documentation](https://docs.pyth.network/pythnet-price-feeds) for more information about Pyth and how to integrate it into your application.
+
+**Warning** this AMM is intended only as a demonstration of Pyth price feeds and is **not for production use**.
+
+## AMM Contract
+
+All of the commands in this section expect to be run from the `contract` directory.
+
+### Building
+
+You need to have [Foundry](https://getfoundry.sh/) and `node` installed to run this example.
+Once you have installed these tools, run the following commands from this directory:
+
+```
+forge install foundry-rs/forge-std@2c7cbfc6fbede6d7c9e6b17afe997e3fdfe22fef --no-git --no-commit
+forge install pyth-network/[email protected] --no-git --no-commit
+forge install OpenZeppelin/[email protected] --no-git --no-commit
+```
+
+### Testing
+
+Simply run `forge test` in the [`contract`](./contract) directory. This command will run the
+tests located in the [`contract/test`](./contract/test) directory.
+
+### Deploying
+
+To deploy the contract, you first need to configure the target network and the tokens in the AMM pool.
+Edit the configuration parameters in the [deploy script](./scripts/deploy.sh) and then run it using `./scripts/deploy.sh`.
+The code comments in that file should help you populate the parameters correctly.
+
+If you don't have ERC-20 tokens to test with, you can use the [token deploy script](./script/deploy_token.sh) to create some for testing.
+Edit the configuration parameters in there before running to set the network and token name.
+This will deploy a new mock token and print out a contract address.
+Once you have this address, you can mint the token anytime using the following command:
+
+```
+cast send --rpc-url <RPC_URL> -l <ERC20_CONTRACT_ADDRESS> "mint(address,uint256)" <YOUR_WALLET_ADDRESS> <QUANTITY_IN_WEI>
+```
+
+When the contract is deployed, the token pools are initially empty.
+You will need to send some funds to the pool for testing purposes.
+You can use the following command to transfer ERC-20 tokens from your wallet to the contract:
+
+```
+cast send --rpc-url <RPC_URL> -l <ERC20_CONTRACT_ADDRESS> "transfer(address,uint256)" <DESTINATION_ADDRESS> <QUANTITY_IN_WEI>
+```
+
+### Create ABI
+
+If you change the contract, you will need to create a new ABI.
+The frontend uses this ABI to create transactions.
+You can overwrite the existing ABI by running the following command:
+
+```
+forge inspect OracleSwap abi > ../app/src/abi/OracleSwapAbi.json
+```
+
+## Frontend Application
+
+All of the commands in this section assume you are in the `app` directory
+
+### Build
+
+`npm ci`
+
+### Run
+
+TODO: describe configuration in this section once the configuration is less janky.
+
+Default configuration:
+
+optimism goerli addresses
+brl 0x8e2a09b54fF35Cc4fe3e7dba68bF4173cC559C69
+usd 0x98cDc14fe999435F3d4C2E65eC8863e0d70493Df
+swap contract 0xf3161b2B32761B46C084a7e1d8993C19703C09e7
+
+Once you've configured everything, simply run `npm run start`.