docs: support detecting broken link cross-projects (#10483)

* docs: support detecting broken link cross-projects

* remove double separators

www/apps/api-reference/next.config.mjs

@@ -2,6 +2,11 @@ import createMDX from "@next/mdx"
 import bundleAnalyzer from "@next/bundle-analyzer"
 import rehypeMdxCodeProps from "rehype-mdx-code-props"
 import rehypeSlug from "rehype-slug"
+import {
+  brokenLinkCheckerPlugin,
+  crossProjectLinksPlugin,
+} from "remark-rehype-plugins"
+import path from "path"
 
 /** @type {import('next').NextConfig} */
 const nextConfig = {
@@ -28,6 +33,48 @@ const nextConfig = {
 const withMDX = createMDX({
   options: {
     rehypePlugins: [
+      [
+        brokenLinkCheckerPlugin,
+        {
+          crossProjects: {
+            docs: {
+              projectPath: path.resolve("..", "book"),
+            },
+            resources: {
+              projectPath: path.resolve("..", "resources"),
+              hasGeneratedSlugs: true,
+            },
+            ui: {
+              projectPath: path.resolve("..", "ui"),
+              contentPath: "src/content/docs",
+            },
+          },
+        },
+      ],
+      [
+        crossProjectLinksPlugin,
+        {
+          baseUrl: process.env.NEXT_PUBLIC_BASE_URL,
+          projectUrls: {
+            docs: {
+              url: process.env.NEXT_PUBLIC_DOCS_URL,
+              path: "",
+            },
+            resources: {
+              url: process.env.NEXT_PUBLIC_RESOURCES_URL,
+            },
+            "user-guide": {
+              url: process.env.NEXT_PUBLIC_USER_GUIDE_URL,
+            },
+            ui: {
+              url: process.env.NEXT_PUBLIC_UI_URL,
+            },
+          },
+          useBaseUrl:
+            process.env.NODE_ENV === "production" ||
+            process.env.VERCEL_ENV === "production",
+        },
+      ],
       [
         rehypeMdxCodeProps,
         {