feat: enhance components with new features and optimizations

- Added support for conditional rendering of the NekoFollower component in AppShell based on ENABLE_NEKO_FOLLOWER.
- Introduced MarkdownImage component in BlogDetailContent for handling images in markdown, supporting both local and external assets.
- Improved BlogToc component to use IntersectionObserver for better performance in tracking active headings.
- Refactored ContentContent to utilize YoutubeLiteEmbed for embedding YouTube videos, simplifying the video rendering logic.
- Created a new YoutubeLiteEmbed component for lazy loading YouTube videos with thumbnail previews.
- Updated site-settings to include ENABLE_NEKO_FOLLOWER constant for feature toggling.
- Enhanced next.config.ts with image optimization settings for better performance.
- Refactored snippets-content to improve code readability and structure.
- Cleaned up home-hero and home-videos-section components for better layout and performance.

next.config.ts

@@ -1,12 +1,19 @@
 import type { NextConfig } from "next";
 
 const nextConfig: NextConfig = {
+  compress: true,
   images: {
+    formats: ["image/avif", "image/webp"],
+    minimumCacheTTL: 60 * 60 * 24 * 30,
     remotePatterns: [
       {
         protocol: "https",
         hostname: "ghchart.rshah.org",
       },
+      {
+        protocol: "https",
+        hostname: "i.ytimg.com",
+      },
     ],
   },
 };