[Documentation] Feature: Add page for supported chains on insight (#5412)

## Problem solved

Short description of the bug fixed or feature added

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---

## PR-Codex overview
This PR introduces a new section in the sidebar for "Supported Chains" and adds a corresponding page with metadata and content in `page.mdx`.

### Detailed summary
- Added a new entry for "Supported Chains" in the sidebar of `sidebar.tsx`.
- Created metadata for the new page in `page.mdx` using `createMetadata`.
- Added a title, description, and image metadata for the "Supported Chains" page.
- Included introductory content and links in `page.mdx`.

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Author: ianthirdweb

apps/portal/src/app/insight/sidebar.tsx

@@ -13,6 +13,10 @@ export const sidebar: SideBar = {
       name: "Get Started",
       href: `${insightSlug}/get-started`,
     },
+    {
+      name: "Supported Chains",
+      href: `${insightSlug}/supported-chains`,
+    },
     {
       name: "Blueprints",
       href: `${insightSlug}/blueprints`,

apps/portal/src/app/insight/supported-chains/page.mdx

@@ -0,0 +1,16 @@
+import { createMetadata } from "@doc";
+
+export const metadata = createMetadata({
+	title: "thirdweb Insight - Supported Chains",
+	description: "List of chains indexed by thirdweb Insight.",
+	image: {
+		title: "thirdweb Insight - Supported Chains",
+		icon: "insight",
+	},
+});
+
+# Supported Chains
+
+[View all chains indexed via thirdweb Insight](https://thirdweb.com/chainlist?service=insight).
+
+If you’d like to suggest a chain for us to support, [contact us](https://thirdweb.com/contact-us).