Make addHabitFunction in store

The issue only must be solved by those who are assigned to it , also don't change any other section not mentioned in the issue , if done the pr will not be accepted

# Habit Tracker Store – README

## Overview

This store manages habits using **Zustand** with middleware (`devtools` and `persist`).

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## Current Status

- `removeHabit` – Implemented
- `toggleHabitCompletion` – Implemented
- `addHabit` – **Declared but not implemented**

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## Action Required

- Implement the **`addHabit` function** inside : src/
│
├── store/
│ └── habitStore.ts # Zustand store for habit management WORK HERE
│
├── components/
│ ├── HabitList.tsx # Displays all habits
│ ├── HabitForm.tsx # Form to add new habits
│ └── HabitItem.tsx # Single habit item component
│
└── App.tsx # Main application component

- Note: The file is in **TypeScript**, so the implementation should follow the `HabitStatesStore` interface.

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