feat: update README and add MIT Licence

LICENCE

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+MIT Licence
+
+Copyright (c) 2026 Zihlu Wang
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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-# React + TypeScript + Vite
+# Delta Force Firearm Modification Codes
 
-This template provides a minimal setup to get React working in Vite.
+Delta Force Firearm Modification Codes is a lightweight web app for browsing and filtering firearm modification codes for Delta Force.
+
+The site is built with Vite, React, TypeScript, Tailwind CSS, and React Router. It presents a searchable code library with filtering by weapon, mode, and tag, and includes quick copy support for each modification code.
+
+## Features
+
+- Browse a curated list of firearm modification codes.
+- Filter results by weapon, mode, and tag.
+- Copy modification codes directly from the interface.
+- Render large lists efficiently with window virtualisation.
+- Deploy as a static site.
+
+## Tech Stack
+
+- Vite
+- React 19
+- TypeScript
+- Tailwind CSS 4
+- React Router 7
+- @tanstack/react-virtual
+- Day.js
+
+## Getting Started
+
+### Prerequisites
+
+- Node.js 20 or later is recommended.
+- pnpm is required for dependency management and scripts.
+
+### Install dependencies
+
+```bash
+pnpm install
+```
+
+### Start the development server
+
+```bash
+pnpm dev
+```
+
+### Build for production
+
+```bash
+pnpm build
+```
+
+### Preview the production build locally
+
+```bash
+pnpm preview
+```
+
+## Available Scripts
+
+- `pnpm dev`: start the Vite development server.
+- `pnpm build`: run TypeScript compilation and create a production build.
+- `pnpm preview`: preview the production bundle locally.
+- `pnpm lint`: run project linting.
+- `pnpm deploy`: build and publish the site with `gh-pages`.
+
+## Project Structure
+
+```text
+src/
+	components/       Shared UI components
+	data/             Modification code dataset
+	init/             Application initialisation
+	layout/           Route layouts
+	page/             Route pages
+	router/           Router configuration
+```
+
+The current dataset is stored in `src/data/modification-codes.json`.
+
+## Deployment
+
+The repository is configured for static deployment. The `public/CNAME` file indicates the site is intended to be served on `onixbyte.dev`.
+
+To deploy:
+
+```bash
+pnpm deploy
+```
+
+## Contributing
+
+Contributions are welcome. If you want to improve the dataset, refine the filtering experience, or fix UI issues, open an issue or submit a pull request.
+
+When contributing, please keep documentation and user-facing copy in British English.
+
+## Licence
+
+This project is released under the MIT Licence. See `LICENCE` for details.