Add 404.mdx with custom error page and navigation to aid users in finding relevant content and support options

Author: Sipher

src/content/docs/404.mdx

@@ -0,0 +1,25 @@
+---
+title: Page Not Found
+description: The page you're looking for doesn't exist
+template: splash
+---
+
+# Whoops! This page doesn't exist
+
+The page you're looking for might have been moved, renamed, or doesn't exist.
+
+## Get back on track
+
+- [Home page](/)
+- [Understanding Torus](/getting-started/understanding-torus/)
+- [How-to Guides](/how-to-guides/table-of-contents/)
+- [Explanations](/explanations/table-of-contents/)
+- [Development](/development/table-of-contents/)
+
+## Need Help?
+
+If you believe this is an error or you were expecting to find something here, please:
+
+- Check the URL for typos
+- Use the search bar to find what you're looking for
+- Visit our [Discord](https://discord.gg/torus) or [Telegram](https://t.me/torusnetwork) for support