Fix web-docs.element.dev deployment (#32922)

* Fix docs

* Switch to vitepress for doc generation

* Run doc build in CI

* Switch docs build to layered

docs/generated/[id].md

@@ -0,0 +1 @@
+<!-- @content -->

docs/generated/[id].paths.ts

@@ -0,0 +1,18 @@
+import genWorkflowMermaid from "../../scripts/gen-workflow-mermaid";
+import { dirname, join } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+
+export default {
+    async paths() {
+        const root = join(__dirname, "..", "..");
+
+        return [
+            {
+                params: { id: "automations" },
+                content: await genWorkflowMermaid([root, join(root, "node_modules", "matrix-js-sdk")]),
+            },
+        ];
+    },
+};