Add dark mode toggle button

[meghanakn473]

Description

i added the dark mode feature to the website

Related Issue

Fixes #351

proof

https://github.com/user-attachments/assets/35a26c61-f029-414d-9ede-6bdeb24a0635

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [X ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• [X ] My code follows the style guidelines of this project
• [X ] I have performed a self-review of my own code
• [X ] I have commented on my code, particularly in hard-to-understand areas
• [ X] I have added tests that prove my fix is effective or that my feature works
• [X ] New and existing unit tests pass locally with my changes
• [ X] Any dependent changes have been merged and published in downstream modules

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Name	Status	Preview	Comments	Updated (UTC)
bio-branch-site	❌ Failed (Inspect)			Nov 6, 2024 4:55pm

[meghanakn473]

@subhadipbhowmik please review and allow merge and kindly assign level 3, gssoc-extd labels.