feat: enhance blog and SEO features with new plugins and metadata

- Introduced rehypeLazyImages plugin for lazy loading images in blog posts.
- Updated sitemap integration to include last modified dates for blog posts.
- Enhanced Head and BaseLayout components to support additional Open Graph metadata.
- Improved RSS feed generation with sanitized content and author information.
- Updated manifest.json for a darker theme and standalone display mode.
- Added support for language-specific attributes in various components.
- Refactored blog post handling to include modified and published timestamps.

src/plugins/rehypeLazyImages.ts

@@ -0,0 +1,13 @@
+import type { Element, Root } from "hast";
+import { visit } from "unist-util-visit";
+
+export default function rehypeLazyImages() {
+	return (tree: Root): void => {
+		visit(tree, "element", (node: Element) => {
+			if (node.tagName !== "img") return;
+			node.properties ??= {};
+			node.properties.loading ??= "lazy";
+			node.properties.decoding ??= "async";
+		});
+	};
+}