feat: add a readme to the surgery package

packages/regenesis-surgery/README.md

 # @eth-optimism/regenesis-surgery
 
-## What is this?
+Scripts used to perform the transition process between OVMv1 and OVMv2.
 
-`regenesis-surgery` contains a series of scripts and tests necessary to perform a regenesis on Optimistic Ethereum.
+## Installation
 
-## Getting started
-
-After cloning and switching to the repository, install dependencies:
-
-```bash
-$ yarn
+```sh
+git clone git@github.com:ethereum-optimism/optimism.git
+yarn clean
+yarn install
+yarn build
 ```
 
-### Configuration
-
-We're using `dotenv` for our configuration.
-To configure the project, clone this repository and copy the `env.example` file to `.env`.
-
-### Runnign scripts
-
-To run an individual script directly:
-
-```bash
-$ npx ts-node scripts/event-indexer.ts
-```
+## Usage
+
+1. Open `.env` and add values for all environment variables listed below.
+2. Run `yarn start` to start the surgery process.
+3. Grab a coffee or something.
+
+## Environment Variables
+
+| Variable                      | Description                                                |
+| ----------------------------- | ---------------------------------------------------------- |
+| `REGEN__STATE_DUMP_FILE`      | Path to the state dump file                                |
+| `REGEN__ETHERSCAN_FILE`       | Path to the etherscan dump file                            |
+| `REGEN__GENESIS_FILE`         | Path to the initial genesis file                           |
+| `REGEN__OUTPUT_FILE`          | Path where the output genesis will be saved                |
+| `REGEN__L2_NETWORK_NAME`      | Name of the L2 network being upgraded (kovan or mainnet)   |
+| `REGEN__L2_PROVIDER_URL`      | RPC provider for the L2 network being upgraded             |
+| `REGEN__L1_PROVIDER_URL`      | RPC provider for the L1 network that corresponds to the L2 |
+| `REGEN__ETH_PROVIDER_URL`     | RPC provider for Ethereum mainnet                          |
+| `REGEN__ROPSTEN_PROVIDER_URL` | RPC provider for the Ropsten testnet                       |
+| `REGEN__ROPSTEN_PRIVATE_KEY`  | Private key of an account that has Ropsten ETH             |
+| `REGEN__STATE_DUMP_HEIGHT`    | Height at which the state dump was taken                   |