Update CONTRIBUTING.md

Author: dadadave80

CONTRIBUTING.md

@@ -1,3 +1,54 @@
-## How to contribute to ERC2535 Diamond Template
+# Contributing to Diamond Lib
 
-#### **Make PR 😀**
+Thanks for your interest in contributing! This is a reusable Foundry library for the [EIP-2535 Diamond Standard](https://eips.ethereum.org/EIPS/eip-2535), so contributions that improve reliability, gas efficiency, or developer experience are welcome.
+
+## Prerequisites
+
+- [Foundry](https://book.getfoundry.sh/getting-started/installation) installed
+- Familiarity with the [EIP-2535 Diamond Standard](https://eips.ethereum.org/EIPS/eip-2535)
+
+## Setup
+
+```sh
+git clone https://github.com/dadadave80/diamond-lib.git
+cd diamond-lib
+forge install
+forge build
+```
+
+## Running Tests
+
+Tests use FFI for selector extraction, so the `--ffi` flag is required:
+
+```sh
+forge test --ffi -vvv
+```
+
+## Making Changes
+
+1. Fork the repo and create a branch from `main`.
+2. Make your changes in the appropriate directory:
+   - `src/facets/` — Facet contracts
+   - `src/libraries/` — Core libraries
+   - `src/interfaces/` — Interfaces
+   - `src/initializers/` — Initializer contracts
+3. Add or update tests in `test/` to cover your changes.
+4. Run `forge fmt` to format your code.
+5. Ensure all tests pass with `forge test --ffi`.
+6. Open a pull request against `main`.
+
+## Guidelines
+
+- Keep gas efficiency in mind — this library is optimized for minimal overhead.
+- Follow existing code style and naming conventions.
+- One logical change per PR — avoid bundling unrelated changes.
+- Include test cases for both success and failure paths.
+
+## Reporting Issues
+
+If you find a bug, please open an issue with:
+- A clear description of the problem
+- Steps to reproduce
+- Expected vs. actual behavior
+
+For security vulnerabilities, please follow the process in [SECURITY.md](SECURITY.md) instead.