website/docs: Update Docusaurus config. Prep for version picker. (#14401)

* website/docs: Clean up config. Add types.

* website/docs: Format MDX.

* website: Fix build warnings. Lint badges frontmatter.

website/types/docusaurus.d.ts

@@ -0,0 +1,45 @@
+/**
+ * @file Supplemental type definitions for Docusaurus.
+ *
+ * @remarks
+ *
+ * Docusaurus uses an unconventional module resolution strategy, which can lead to
+ * issues when using TypeScript.
+ *
+ * The types in this file are intended to expose less visible types to TypeScript's
+ * project references, allowing for better type checking and autocompletion.
+ */
+
+declare module "@docusaurus/plugin-content-docs-types" {
+    export * from "@docusaurus/plugin-content-docs";
+    export * from "@docusaurus/plugin-content-docs/src/types.ts";
+    export * from "@docusaurus/plugin-content-docs/src/sidebars/types.ts";
+}
+
+declare module "@docusaurus/plugin-content-docs/src/sidebars/types" {
+    export * from "@docusaurus/plugin-content-docs/src/sidebars/types.ts";
+}
+
+declare module "@docusaurus/plugin-content-docs/client" {
+    import { DocContextValue as BaseDocContextValue } from "@docusaurus/plugin-content-docs/lib/client/doc.js";
+    import { DocFrontMatter as BaseDocFrontMatter } from "@docusaurus/plugin-content-docs";
+
+    /**
+     * @monkeypatch
+     */
+    export interface DocFrontMatter extends BaseDocFrontMatter {
+        support_level?: string;
+        authentik_version?: string;
+        authentik_preview: boolean;
+        authentik_enterprise: boolean;
+    }
+
+    export interface DocContextValue extends BaseDocContextValue {
+        /**
+         * @monkeypatch
+         */
+        frontMatter: DocFrontMatter;
+    }
+
+    export function useDoc(): DocContextValue;
+}