Add LinkedIn to social links

Adds linkedin.com to the socialLinks array in site.config.ts.
The LinkedIn icon now appears on the contact page, blog index,
blog post pages, header, and footer automatically.

https://claude.ai/code/session_019mp7rTrQPx9yxp17hgjsYb

src/config/site.config.ts

@@ -75,6 +75,7 @@ const siteConfig: SiteConfig = {
   socialLinks: [
     'https://github.com/hansmartens68/Astro-Rocket',
     'https://x.com/hansmartens_dev',
+    'https://www.linkedin.com',
   ],
   twitter: {
     site: 'https://x.com/hansmartens_dev',