add contributing guidelines

CONTRIBUTING.md

@@ -0,0 +1,84 @@
+# Contributing
+
+Welcome! We're glad you're interested in contributing to the project.
+
+We welcome contributions of any kind; however, for **feature changes or additions**, please open an issue first for discussion.
+
+## Getting Started
+
+To get started, [fork this repository](https://github.com/nizewn/chessu/fork) to your GitHub account. You can then clone the repository to your local machine and create a new branch for your changes.
+
+```sh
+git clone https://github.com/[your-username]/chessu.git
+cd chessu
+git checkout -b my-feature-branch
+```
+
+## Development
+
+> Node.js 18 or newer is recommended.
+
+This project is structured as a monorepo using npm workspaces, separated into three packages:
+
+- `client` - Next.js application for the front-end, deployed to [ches.su](https://ches.su) via Vercel.
+- `server` - Node/Express.js application for the back-end, deployed to [server.ches.su](https://server.ches.su) via Railway.
+- `types` - Shared type definitions required by the client and server.
+
+### Running the project
+
+1. Install the necessary dependencies by running `npm install` in the root directory of the project.
+2. In the `server` directory, create a `.env` file for your PostgreSQL database. You can try [ElephantSQL](https://www.elephantsql.com/) or [Aiven](https://aiven.io/postgresql) for a free hosted database.
+   ```env
+   PGHOST=db.example.com
+   PGUSER=exampleuser
+   PGPASSWORD=examplepassword
+   PGDATABASE=chessu
+   ```
+3. Run the development servers with `npm run dev`.
+   - To run the frontend and backend servers separately, use `npm run dev -w client` and `npm run dev -w server`, respectively.
+4. You can access the frontend at http://localhost:3000 and the backend at http://localhost:3001.
+5. You may now make your changes and commit them to your branch.
+
+When adding new dependencies or running other commands from the root directory, you can specify the workspace with the `-w` flag. For example, `npm run build -w client` or `npm install express -w server`.
+
+### Formatting and linting
+
+We use ESLint and Prettier to enforce code style and formatting. Please make sure to run `npm run lint-fix` and `npm run format` before committing your changes.
+
+### Environment variables
+
+You may create a `.env` file in each package directory to set their environment variables.
+
+<details>
+<summary>client</summary>
+
+```env
+NEXT_PUBLIC_API_URL=http://localhost:3001 # replace with backend URL
+```
+
+</details>
+
+<details>
+<summary>server</summary>
+
+```env
+CORS_ORIGIN=http://localhost:3000 # replace with frontend URL
+PORT=3001
+SESSION_SECRET=randomstring # replace for security
+
+# PostgreSQL connection info (required)
+PGHOST=db.example.com
+PGUSER=exampleuser
+PGPASSWORD=examplepassword
+PGDATABASE=chessu
+```
+
+</details>
+
+## Guidelines
+
+- Follow the [Code of Conduct](CODE_OF_CONDUCT.md).
+- Make sure your changes are thoroughly tested.
+- Keep your commits atomic and descriptive.
+- Ensure that your code is formatted and linted using `npm run lint-fix` and `npm run format`.
+- Make your pull requests as descriptive as possible.