fixed icon alignment in index.html

[kaushikharsh99]

Description

We fixed the alignment of the GitHub icon in the sidebar of index.html.
Previously, the icon was not properly centered at the bottom of the sidenav.
Now, it stays perfectly aligned horizontally and positioned at the bottom for a cleaner and more consistent layout.

Related Issue

Fixes #16

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if any)
• My changes generate no new warnings
• I have tested that the icon alignment works properly across screen sizes
• Any dependent changes have been merged and published in downstream modules
• I have added all the three reviewers: @vinitshahdeo, @Kashish121 & @ishika1727