Add SEO optimization (meta tags, sitemap, structured data)

[AmitoVrito]

Description

Optimize docs site for search engines.

What to do

• Ensure proper title, tagline, url in docusaurus.config.ts
• Add meta descriptions to key pages
• Enable @docusaurus/plugin-sitemap
• Add JSON-LD structured data for SoftwareApplication
• Submit sitemap to Google Search Console

[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!