Add missing yarn clean for frontend

.changeset/eight-experts-visit.md

@@ -0,0 +1,13 @@
+---
+'@backstage/create-app': patch
+---
+
+Add missing `yarn clean` for app.
+
+For users with existing Backstage installations, add the following under the `scripts` section in `packages/app/package.json`, after the "lint" entry:
+
+```json
+"clean": "backstage-cli clean",
+```
+
+This will add the missing `yarn clean` for the generated frontend.

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

@@ -46,6 +46,7 @@
     "build": "backstage-cli app:build",
     "test": "backstage-cli test",
     "lint": "backstage-cli lint",
+    "clean": "backstage-cli clean",
     "test:e2e": "cross-env PORT=3001 start-server-and-test start http://localhost:3001 cy:dev",
     "test:e2e:ci": "cross-env PORT=3001 start-server-and-test start http://localhost:3001 cy:run",
     "cy:dev": "cypress open",