Add content to README file (#3)

Add 'Getting Started' and 'Contribution Guidelines' sections to `README.md`.

* **Getting Started**
  - Add prerequisites including Node.js v22 and npm.
  - Add installation instructions for cloning the repository, installing dependencies, and creating a `.env` file.
  - Add instructions for running the bot using `npm run start`.

* **Contribution Guidelines**
  - Add coding standards including following existing code style, using meaningful names, and writing comments.
  - Add instructions for creating issues with clear descriptions and steps to reproduce.
  - Add instructions for submitting pull requests including forking the repository, creating a new branch, testing changes, and providing a clear description.