Add README

Author: Mauro Lacy

README.md

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+# Op-finality-gadget
+
+This repo contains the Wasm smart contract for Optimism staking integration.
+It will be deployed on Babylon, and will maintain finality signatures and block finalisation status of Optimism rollups.
+
+## Development
+
+### Prerequisites
+
+Make sure you have `cargo-run-script` installed and docker running.
+
+```bash
+cargo install cargo-run-script
+```
+
+### Clean the build
+
+```bash
+cargo clean
+```
+
+### Build the contract
+
+```bash
+cargo build
+```
+
+### Formatting and Linting
+
+Check whether the code is formatted correctly.
+
+```bash
+cargo fmt --all -- --check
+cargo check
+cargo clippy --all-targets -- -D warnings
+```
+
+Alternatively, you can run the following command to run all the checks at once.
+
+```bash
+cargo run-script lint
+```
+
+### Test the contract
+
+Note: Requires the optimized contract to be built (`cargo optimize`)
+
+Runs all the CI checks locally (in your actual toolchain).
+
+```bash
+cargo test --lib
+```
+
+### Integration tests the contract
+
+Note: Requires the optimized contract to be built (`cargo optimize`)
+
+```bash
+cargo test --test integration
+```
+
+Alternatively, you can run the following command, that makes sure to build the optimized contract before running
+the integration tests.
+
+```bash
+cargo run-script integration
+```
+
+### Build the optimized contract
+
+```bash
+cargo run-script optimize
+```