create-app: add app-defaults dependency to app + notice in changeset

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

.changeset/hot-walls-fail.md

@@ -4,7 +4,7 @@
 
 Migrated the app template use the new `@backstage/app-defaults` for the `createApp` import, since the `createApp` exported by `@backstage/app-core-api` will be removed in the future.
 
-To migrate an existing application, make the following change to `packages/app/src/App.tsx`:
+To migrate an existing application, add the latest version of `@backstage/app-defaults` as a dependency in `packages/app/package.json`, and make the following change to `packages/app/src/App.tsx`:
 
 ```diff
 -import { createApp, FlatRoutes } from '@backstage/core-app-api';

packages/create-app/src/lib/versions.ts

@@ -30,6 +30,7 @@ Rollup will extract the value of the version field in each package at build time
 leaving any imports in place.
 */
 
+import { version as appDefaults } from '../../../app-defaults/package.json';
 import { version as backendCommon } from '../../../backend-common/package.json';
 import { version as catalogClient } from '../../../catalog-client/package.json';
 import { version as catalogModel } from '../../../catalog-model/package.json';
@@ -68,6 +69,7 @@ import { version as pluginTechdocsBackend } from '../../../../plugins/techdocs-b
 import { version as pluginUserSettings } from '../../../../plugins/user-settings/package.json';
 
 export const packageVersions = {
+  '@backstage/app-defaults': appDefaults,
   '@backstage/backend-common': backendCommon,
   '@backstage/catalog-client': catalogClient,
   '@backstage/catalog-model': catalogModel,

packages/create-app/templates/default-app/packages/app/package.json.hbs

@@ -4,6 +4,7 @@
   "private": true,
   "bundled": true,
   "dependencies": {
+    "@backstage/app-defaults": "^{{version '@backstage/app-defaults'}}",
     "@backstage/catalog-model": "^{{version '@backstage/catalog-model'}}",
     "@backstage/cli": "^{{version '@backstage/cli'}}",
     "@backstage/core-app-api": "^{{version '@backstage/core-app-api'}}",