feat: add language switcher component and update layout

- Introduced a new LanguageSwitcher component to facilitate language switching in the application.
- Added an SVG icon for the language switcher button.
- Updated the Header component to adjust margin for better spacing.
- Modified the Navigation component's margin and top properties for improved layout.
- Adjusted the ThemeToggle button size for consistency with the new design.

src/components/Header.astro

@@ -14,7 +14,7 @@ const marginClass = {
 
 <header>
   <h1
-    class={`${marginClass} mt--1.6 text-12 c-primary font-bold font-title`}
+    class={`${marginClass} mt--3.2 text-12 c-primary font-bold font-title`}
     aria-label="Title Tag"
   >
     <a href="/">