Create README.md

Author: SuRu190

task12-mark-list-as-completed/README.md

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+# Task 12 – Mark List as Completed
+
+## ✅ Objective:
+Add a "completed" visual class to a task when it's clicked, and allow toggling it back.
+
+## 💡 Concepts Practiced:
+- `classList.toggle`
+- Adding event listeners to dynamic list items
+
+## 📘 What I Learned:
+- How to add and toggle class on dynamic elements.
+- Creating a visual difference between completed and active tasks.
+
+## ▶️ Example Flow:
+1. Click on task “Clean Room”.
+2. Task gets line-through and turns gray.
+3. Click again → returns to normal.