feat: Add application screenshot to README

This commit adds a screenshot of the application to the `README.md` file to provide a visual preview for users and developers.

Author: Coding-Meet

README.md

@@ -1,5 +1,7 @@
 # 🧩 Git Backup Hub
 
+[![Git Backup Hub ](screenshot/git_backup_hub.png)]()
+
 **Git Backup Hub** is a cross-platform desktop application built with **Kotlin Multiplatform** and **Compose for Desktop**, designed to help developers easily back up their GitHub repositories — both public and private — with progress tracking and elegant UI.
 
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