Add docs for the routes API

packages/registry/docs/how-to-guides/register-routes.md

@@ -0,0 +1,54 @@
+---
+myst:
+  html_meta:
+    "description": "How to register new routes in @plone/registry"
+    "property=og:description": "How to register new routes in @plone/registry"
+    "property=og:title": "How to register new routes"
+    "keywords": "Volto, Plone, frontend, React, configuration, routes, React Router"
+---
+
+# How to register new routes
+
+````{admonition} Warning! This feature is experimental and only applies to register routes for React Router 7 applications. Click to accept the risks and read details.
+:class: warning
+
+The `config.registerRoute` method will add a new route to the configuration registry.
+This route is intended to be loaded by the `@plone/react-router` helper and loaded in a React Router 7 app.
+Under the hood, it saves the routes in the `config.routes` key in the configuration object.
+You should provide one route at a time and should have this shape:
+
+```ts
+type ReactRouterRouteEntry = {
+  type: 'route' | 'index' | 'layout' | 'prefix';
+  path: string;
+  file: string;
+  options?: {
+    id?: string;
+    index?: boolean;
+    caseSensitive?: boolean;
+  };
+  children?: ReactRouterRouteEntry[];
+};
+```
+
+The `type`, `path` and `file` are mandatory.
+The `type` key specify the route type to be created, more specifically, one of `route`, `index`, `layout` or `prefix`.
+The type `route` can contain nested routes.
+Check the official [React Router 7 documentation](https://reactrouter.com/start/framework/routing) for more information on how to define React Router 7 routes.
+
+You register a route like this:
+
+```ts
+config.registerRoute({
+  type: 'route',
+  path: '/login',
+  file: '@plone/cmsui/components/login.tsx',
+  options: {
+    id: 'login',
+    index: true,
+  },
+});
+```
+
+It is required that you set the full module path name for the registered route component in order to make `@plone/registry` to it address correctly when it's going to be used.
+````