fix: Explicitly install 'pretty-format'

Work around for testing-library/react-testing-library#694

Author: losvedir

assets/package-lock.json

@@ -49,6 +49,7 @@
     "node-sass": "^4.14.1",
     "optimize-css-assets-webpack-plugin": "^5.0.1",
     "prettier": "^2.0.5",
+    "pretty-format": "^26.0.1",
     "sass-loader": "^8.0.2",
     "source-map-loader": "^1.0.0",
     "terser-webpack-plugin": "^3.0.3",