Adding build:dev script for spectrum testing.

- In `spectrum`:
```bash
cp ../search/search.local.tar.gz ./
gtar -xzf search.local.tar.gz -C public --transform=s%search/index.html%search/app.html% --strip-components=1
```

.gitignore

@@ -8,6 +8,7 @@ coverage
 
 # production
 build
+*.tar.gz
 
 # misc
 .DS_Store

package.json

@@ -54,6 +54,7 @@
   },
   "scripts": {
     "build": "react-scripts build",
+    "build:dev": "CI=false REACT_APP_LOGIN_BASE_URL=http://localhost:3000 REACT_APP_SPECTRUM_BASE_URL=http://localhost:3000/spectrum npm run build && gtar -C build --transform s/./search/ -czf search.local.tar.gz .",
     "develop": "npm run start",
     "eject": "react-scripts eject",
     "lint": "npx eslint src/**/*.js",