Added contribution notes and guidelines

Author: Sidatii

CONTRIBUTING.md

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+
+---
+
+# Contributing to xpscan 🚀
+
+First of all, thank you for showing interest in contributing to **xpscan**! Community contributions are what make open-source tools robust and reliable.
+
+Whether you are fixing a bug, improving documentation, or adding a new feature, your help is appreciated. Please take a moment to review this guide to ensure a smooth contribution process.
+
+---
+
+## 🏗️ Project Architecture Overview
+
+Before you dive into the code, it helps to understand how the project is organized. We follow a modular design to keep the networking logic separate from the file management.
+
+* **Scanner:** Handles the networking logic (non-blocking sockets).
+* **Exporter:** Handles saving results to the disk.
+* **Common:** Shared data structures (like the `PortResult` struct).
+* **Tests:** Unit tests using CRITERION to ensure stability.
+
+---
+
+## 🛠️ How to Get Started
+
+### 1. Prerequisites
+
+You will need the following tools on your machine:
+
+* **C++ Compiler** (supporting C++17 or later)
+* **CMake** (version 3.10+)
+* **Git**
+* **Criterion** (usually fetched automatically via CMake)
+
+### 2. Setting Up Your Local Environment
+
+1. **Fork** the repository on GitHub.
+2. **Clone** your fork locally:
+```bash
+git clone https://github.com/your-username/xpscan.git
+cd xpscan
+
+```
+
+
+3. **Build** the project to make sure everything is working:
+```bash
+mkdir build && cd build
+cmake ..
+make
+
+```
+
+
+
+---
+
+## 🧪 Development Rules
+
+### 1. Writing Tests
+
+We use **Mocking** to test the scanner without actually hitting the network and to test the exporter without actually writing to the disk.
+
+* If you add a new feature, please add a test in `tests/ScannerTest.cpp`.
+* Run tests using: `ctest` or `./xpscan_tests`.
+
+### 2. Performance First
+
+`xpscan` is designed to be fast.
+
+* Avoid blocking calls.
+* Always use the `O_NONBLOCK` flag for new networking features.
+* Respect the 200ms timeout window to prevent the tool from "hanging."
+
+### 3. Code Style
+
+* Use descriptive variable names.
+* Comment complex logic, especially around bitwise operations or socket configurations.
+* Keep functions small and focused on a single task.
+
+---
+
+## 📬 Submitting Your Changes
+
+### Step 1: Create a Branch
+
+Always create a new branch for your work:
+
+```bash
+git checkout -b feature/your-feature-name
+
+```
+
+### Step 2: Commit Your Changes
+
+Write clear, concise commit messages:
+
+* `feat: add XML export support`
+* `fix: resolve memory leak in scanner`
+* `docs: update installation instructions`
+
+### Step 3: Push and Open a Pull Request (PR)
+
+1. Push your branch to your fork: `git push origin feature/your-feature-name`.
+2. Open a Pull Request on the main repository.
+3. Fill out the **PR Template** provided (it will pop up automatically).
+4. Wait for a maintainer to review your code!
+
+---
+
+## 📜 Code of Conduct
+
+By participating in this project, you agree to maintain a respectful and inclusive environment. Please be kind to other contributors!
+
+---