feat(i18n): add internationalization support with astro-i18next

- Add astro-i18next package for i18n support
- Create LanguageSwitcher component with English and Chinese options
- Add i18n guide documentation
- Update .gitignore and package.json

src/components/GlassHeader.tsx

@@ -1,4 +1,5 @@
 import ThemeToggle from "./ui/theme-toggle";
+import LanguageSwitcher from "./LanguageSwitcher"; // Added import for LanguageSwitcher
 import { personalInfo } from "@/lib/data";
 import { useState } from "react";
 import { Menu, X } from "lucide-react";
@@ -46,9 +47,11 @@ export default function GlassHeader() {
         </nav>
 
         <div className="flex items-center space-x-2">
+          {/* Language Switcher added here */}
+          <LanguageSwitcher />
           <ThemeToggle />
 
-          {/* Mobile Menu Button */}
+          {/* Mobile Menu Button */}          
           <motion.button
             className="md:hidden p-2 text-foreground"
             onClick={toggleMenu}