Add Dynamic Background with Parallax Effect

[DIYA-BHATT29]

📌 Description

This PR enhances the visual experience of the Flappy Bird game by introducing a dynamic background system. The background now includes animated clouds, moving mountains, and a gradient sky that transitions from day to evening to night as the player's score increases. A smooth parallax effect is implemented to create depth and make the gameplay feel more immersive.

🔗 Related Issue

Closes: #49

---

🛠 Changes Made

Added animated cloud layer with smooth horizontal movement.
Implemented moving mountain layer to create a parallax depth effect.
Added gradient sky that transitions from Day → Evening → Night based on player score.
Introduced a new background rendering function to draw sky, clouds, and mountains before other game elements.
Ensured the new background system integrates without affecting existing gameplay mechanics.

📷 Screenshots (if applicable)

---

✅ Checklist

• [✅ ] I have tested my changes
• [ ✅] My code follows project guidelines
• [ ✅] I have linked the related issue

[FOSSCLUB-LBSITW]

Hi @DIYA-BHATT29, thanks for the contribution! The PR looks great, but there is a merge conflict in script.js with the main branch. Could you please resolve the conflict and update the branch so we can proceed with the merge?