feat: integrate MEV metrics widget into navbar

Add custom navbar item type to support the MEV metrics widget and configure
it in the navbar. The widget displays real-time MEV and gas refund data
fetched from the Dune Analytics API.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: odysseus0

docusaurus.config.js

@@ -69,6 +69,10 @@ module.exports = async function createConfigAsync() {
               sidebarId: 'api',
               position: 'left',
             },
+            {
+              type: 'custom-mevMetrics',
+              position: 'right',
+            },
             {
               href: 'https://github.com/flashbots/docs',
               label: 'GitHub',

src/theme/NavbarItem/ComponentTypes.tsx

@@ -0,0 +1,27 @@
+import DefaultNavbarItem from '@theme/NavbarItem/DefaultNavbarItem';
+import DropdownNavbarItem from '@theme/NavbarItem/DropdownNavbarItem';
+import LocaleDropdownNavbarItem from '@theme/NavbarItem/LocaleDropdownNavbarItem';
+import SearchNavbarItem from '@theme/NavbarItem/SearchNavbarItem';
+import HtmlNavbarItem from '@theme/NavbarItem/HtmlNavbarItem';
+import DocNavbarItem from '@theme/NavbarItem/DocNavbarItem';
+import DocSidebarNavbarItem from '@theme/NavbarItem/DocSidebarNavbarItem';
+import DocsVersionNavbarItem from '@theme/NavbarItem/DocsVersionNavbarItem';
+import DocsVersionDropdownNavbarItem from '@theme/NavbarItem/DocsVersionDropdownNavbarItem';
+import MevMetrics from '@site/src/components/MevMetrics';
+
+import type {ComponentTypesObject} from '@theme/NavbarItem/ComponentTypes';
+
+const ComponentTypes: ComponentTypesObject = {
+  default: DefaultNavbarItem,
+  localeDropdown: LocaleDropdownNavbarItem,
+  search: SearchNavbarItem,
+  dropdown: DropdownNavbarItem,
+  html: HtmlNavbarItem,
+  doc: DocNavbarItem,
+  docSidebar: DocSidebarNavbarItem,
+  docsVersion: DocsVersionNavbarItem,
+  docsVersionDropdown: DocsVersionDropdownNavbarItem,
+  'custom-mevMetrics': MevMetrics,
+};
+
+export default ComponentTypes;