docs-util: added a namespaces plugin (#8500)

Added a namespaces plugin that allows generating namespaces and automatically adds reflections in a path pattern to the namespace.

This is particularly useful for the workflows reference, as workflows under the `**/packages/core/core-flows/**/workflows/**` path pattern are shown under a Workflows title, and steps under the path pattern `**/packages/core/core-flows/**/steps/**` are shown under a Steps title.

www/utils/packages/utils/src/workflow-utils.ts

@@ -2,7 +2,7 @@ import { SignatureReflection } from "typedoc"
 
 export function isWorkflow(reflection: SignatureReflection): boolean {
   return (
-    reflection.parent.children?.some((child) => child.name === "runAsStep") ||
+    reflection.parent?.children?.some((child) => child.name === "runAsStep") ||
     false
   )
 }