chore: backend-middleware is a pre-requisite of test app

* The backend-middleware package must be compiled prior to starting the
  test app

package.json

@@ -14,7 +14,7 @@
   ],
   "scripts": {
     "start": "concurrently -n hawtio,app \"yarn build:hawtio:watch\" \"yarn start:app\"",
-    "start:app": "yarn workspace app start",
+    "start:app": "yarn build:backend-middleware && yarn workspace app start",
     "build": "yarn build:hawtio",
     "build:all": "yarn workspaces foreach -v -Aipt --exclude @hawtio/next-root run build",
     "build:app": "yarn workspace app build",