api-docs: add default route target

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/chilled-planes-sniff.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-api-docs': patch
+---
+
+The `registerComponent` external route will now by default bind to the catalog import page if it is available.

plugins/api-docs/src/routes.ts

@@ -26,4 +26,5 @@ export const rootRoute = createRouteRef({
 export const registerComponentRouteRef = createExternalRouteRef({
   id: 'register-component',
   optional: true,
+  defaultTarget: 'catalog-import.importPage',
 });