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/env.d.ts

@@ -0,0 +1,9 @@
+/// <reference path="../.astro/types.d.ts" />
+interface ImportMetaEnv {
+	readonly DEFAULT_TITLE: string;
+	readonly DEFAULT_DESCRIPTION: string;
+}
+
+interface ImportMeta {
+	readonly env: ImportMetaEnv;
+}