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/pages/blog/[...slug].astro

@@ -24,6 +24,7 @@ const { Content, remarkPluginFrontmatter } = await post.render();
 const date = dayjs(post.data.pubDate.toString()).format("MMMM DD, YYYY");
 const title = `${post.data.title} | Valentin Popov`;
 const description = post.data.description;
+const lang = post.data.lang;
 ---
 
 <style lang="scss">
@@ -34,7 +35,7 @@ const description = post.data.description;
 	}
 </style>
 
-<Layout title={title} description={description}>
+<Layout title={title} description={description} lang={lang}>
 	<article>
 		<section>
 			<h1>{post.data.title}</h1>
@@ -44,7 +45,7 @@ const description = post.data.description;
 			<p>
 				<small>
 					Posted
-					<time datetime={post.data.pubDate.toISOString()}>{date}</time>
+					<time datetime={post.data.pubDate.toISOString()} lang="en">{date}</time>
 					by&nbsp;{post.data.author}
 					<span>&nbsp;•&nbsp;</span>
 					<span>{remarkPluginFrontmatter.minutesRead}</span>