feat: enhance accessibility and language support across components

- Updated various components to include `lang` attributes for improved accessibility and SEO.
- Introduced a new `env.d.ts` file to define environment variables for better type safety.
- Adjusted the print width in `.prettierrc.mjs` for improved code formatting.
- Streamlined the `Header`, `PostElement`, and `SocialLinks` components for better structure and clarity.
- Added language support to blog posts and updated the layout to reflect these changes.

src/content/config.ts

@@ -8,6 +8,7 @@ const blog = defineCollection({
 		draft: z.optional(z.boolean()),
 		pubDate: z.coerce.date(),
 		title: z.string(),
+		lang: z.string(),
 	}),
 });