allow config option on custom pages (keystonejs#2415)

.changeset/light-mirrors-train.md

@@ -0,0 +1,19 @@
+---
+'@keystonejs/app-admin-ui': minor
+---
+
+Allowed use of `config` object in custom pages. This enables passing on any custom config or even a function to the custom Page component in `admin-ui`
+
+you can now add config like this
+
+```js
+{
+  label: 'About this project',
+  path: 'about',
+  config: {
+    option: 'value',
+  },
+  component: About,
+},
+
+```

packages/app-admin-ui/client/index.js

@@ -36,10 +36,11 @@ export const KeystoneAdminUI = () => {
       .filter(page => typeof page.path === 'string')
       .map(page => {
         const Page = page.component;
+        const config = page.config || {};
         return {
           path: `${adminPath}/${page.path}`,
           component: () => {
-            return <Page />;
+            return <Page {...config} />;
           },
           exact: true,
         };