create-app: add missing @backstage/plugin-api-docs entry to plugins.ts (#3257)

.changeset/lucky-lemons-return.md

@@ -0,0 +1,5 @@
+---
+'@backstage/create-app': patch
+---
+
+Fix missing api-docs plugin registration in app template

packages/create-app/templates/default-app/packages/app/src/plugins.ts

@@ -1,3 +1,4 @@
+export { plugin as ApiDocs } from '@backstage/plugin-api-docs';
 export { plugin as CatalogPlugin } from '@backstage/plugin-catalog';
 export { plugin as RegisterComponent } from '@backstage/plugin-register-component';
 export { plugin as ScaffolderPlugin } from '@backstage/plugin-scaffolder';