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/components/PostElement.astro

@@ -25,10 +25,10 @@ const formattedDate = dayjs(post.data.pubDate.toString()).format("MMMM DD, YYYY"
 </style>
 
 <li>
-	<a href={`/blog/${post.slug}`}>{post.data.title}</a>
+	<a href={`/blog/${post.slug}`} lang={post.data.lang}>{post.data.title}</a>
 	<div>
 		<small>
-			<time datetime={post.data.pubDate.toISOString()}>{formattedDate}</time>
+			<time datetime={post.data.pubDate.toISOString()} lang="en">{formattedDate}</time>
 			<span>•</span>
 			<span>{remarkPluginFrontmatter.minutesRead}</span>
 		</small>