Add SVG assets and TypeScript configuration

- Created a new SVG for the Open Graph image (og-image.svg) with a gradient background and text elements.
- Added Vercel logo SVG (vercel.svg) for deployment branding.
- Introduced a window icon SVG (window.svg) for UI representation.
- Initialized TypeScript configuration file (tsconfig.json) with strict settings and module resolution for a React project.

app/sitemap.ts

@@ -0,0 +1,13 @@
+import type { MetadataRoute } from "next";
+
+export default function sitemap(): MetadataRoute.Sitemap {
+  const siteUrl = process.env.NEXT_PUBLIC_SITE_URL || "https://blocnote.arthurp.fr";
+  return [
+    {
+      url: siteUrl,
+      lastModified: new Date(),
+      changeFrequency: "weekly",
+      priority: 1.0,
+    },
+  ];
+}