docs: Add IntelliJ GitHub Copilot Tutorial (Sections 1–5 with images)

tutorials/intellijCopilot.md

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+<frontmatter>
+title: "IntelliJ IDEA – Using GitHub Copilot"
+pageNav: 2
+</frontmatter>
+
+# IntelliJ IDEA – Using GitHub Copilot
+
+GitHub Copilot is an AI-powered code assistant that helps you write, test, and refactor code faster. In this tutorial, you’ll learn how to set up and use Copilot in IntelliJ IDEA — perfect for students in CS2103/T, CS2113, and other Java-heavy modules.
+
+<box type="info" seamless>
+To use GitHub Copilot for free as a student, you must:
+
+1. Sign up for a GitHub account  
+2. Enable two-factor authentication (2FA)  
+3. Apply for the GitHub Student Developer Pack  
+
+This guide walks you through setting up Copilot access and using it in IntelliJ IDEA.
+</box>
+
+---
+
+## 1. Setting Up GitHub Copilot Access
+
+### Step 1: Fill in Billing Information
+
+1. Visit the [GitHub billing settings page](https://github.com/settings/billing).  
+2. Fill in only your billing address (no charges will occur if you qualify for student access).  
+3. Click **Save billing information**.
+
+<img src="images/intellijcopilot/copilot-billing-settings.jpeg" alt="Billing Settings Page" width="60%" />
+
+### Step 2: Enable Two-Factor Authentication (2FA)
+
+1. Go to [GitHub security settings](https://github.com/settings/security).  
+2. Click **Enable two-factor authentication** and follow the prompts.  
+3. Use an authenticator app (e.g., Google Authenticator, Microsoft Authenticator) to complete setup.
+
+<img src="images/intellijcopilot/github-2fa-settings.jpeg" alt="2FA Settings Page" width="60%" />
+
+### Step 3: Link Your University Email
+
+1. Go to [GitHub email settings](https://github.com/settings/emails).  
+2. Add your university email (e.g., yourname@u.nus.edu).  
+3. Verify via the confirmation link sent to your inbox.
+
+<pic src="tutorials/images/intellijcopilot/link-university-email.png" width="500" />
+
+### Step 4: Apply for GitHub Student Developer Pack
+
+1. Visit the [GitHub Education Pack page](https://education.github.com/pack).  
+2. Click **Get student benefits** and complete the application.  
+3. After approval, you’ll see a message like “You already have the Student Developer Pack.”
+
+<img src="images/intellijcopilot/copilot-education-pack.jpeg" alt="Student Pack Confirmation" width="60%" />
+
+---
+
+## 2. Installing GitHub Copilot Plugin in IntelliJ IDEA
+
+1. Open IntelliJ IDEA.  
+2. On Mac: **IntelliJ IDEA > Preferences**. On Windows/Linux: **File > Settings**.  
+3. Select **Plugins > Marketplace**.  
+4. Search for **GitHub Copilot**.  
+<img src="images/intellijcopilot/intellij-search-copilot.png" alt="Search GitHub Copilot Plugin" width="60%" />
+5. Click **Install**, then **Restart IDE** when prompted.
+<img src="images/intellijcopilot/intellij-restart-prompt.png" alt="Restart Prompt" width="60%" />
+
+
+---
+
+## 3. Signing In to GitHub
+
+1. After restart, open **Settings > Languages & Frameworks > GitHub Copilot**.  
+2. Under **Authentication**, click **Manage GitHub Accounts**.  
+3. Sign in via your browser and authorize Copilot.  
+4. Your GitHub username should appear in the **Preferred GitHub account** dropdown.
+
+<img src="images/intellijcopilot/intellij-copilot-settings.png" alt="Copilot Settings in IntelliJ" width="60%" />
+
+
+---
+
+## 4. Verifying Copilot in Action
+
+1. Create or open a Java file, e.g., `CopilotTest.java`.  
+2. Inside a `main` method, type:
+
+```java
+// print Hello World
+```
+
+3. Wait 2–3 seconds — a gray suggestion appears.  
+4. Press **Tab** to accept the suggestion.
+
+<img src="images/intellijcopilot/copilot-suggestion-visible.png" alt="Copilot Suggestion Appears" width="60%" />
+<img src="images/intellijcopilot/copilot-accepted-fixed.png" alt="Copilot Suggestion Example" width="60%" />
+
+<box type="tip" seamless>
+Copilot works best with clear, descriptive comments.
+</box>
+
+---
+
+## 5. Using Copilot Chat *(if available)*
+
+> Copilot Chat may be in beta or limited in IntelliJ.
+
+1. Go to **View > Tool Windows > Copilot Chat**.  
+2. Ask a question, e.g.:
+
+```java
+Write a function to reverse a string in Java.
+```
+
+3. Review the response and insert code as needed.
+
+<img src="images/intellijcopilot/copilot-chat-window.png" alt="Copilot Chat Window" width="60%" />
+
+---
+
+## 6. Troubleshooting
+
+<box type="tip" seamless>
+**Common Issues & Fixes**  
+
+- **No suggestions** → Ensure the plugin is enabled and you’re signed in.  
+- **No Copilot panel** → Restart IntelliJ or reinstall the plugin.  
+- **Unsupported file type** → Use `.java` or other supported languages.  
+- **Authentication errors** → Re-authorize in **Settings > GitHub Copilot**.  
+</box>
+
+---
+
+**Contributors:** Arshin Sikka (@arshinsikka)