Add mobile-responsive hamburger menu

[AmitoVrito]

Description

Verify sidebar works on mobile, fix any overflow or styling issues.

What to do

• Test on various screen sizes (iPhone, iPad, Android)
• Fix any overflow or styling issues
• Ensure code blocks are horizontally scrollable on mobile

[AmitoVrito]

Thanks for your interest! I will assign it to you. Before you start, could you give the repo a ⭐ on the main repo (https://github.com/SynapseKit/SynapseKit)? It really helps with visibility for a new project. Looking forward to your PR!