Update the CSS transition for breadcrumbs

The actual transition length might need adjusting, but this is fairly close to what was requested.

package.json

@@ -94,6 +94,7 @@
     "react-dom": "^16.9.0",
     "react-focus-lock": "^2.2.1",
     "react-resizable": "^1.10.1",
+    "react-transition-group": "^4.4.1",
     "resize-observer-polyfill": "^1.5.0",
     "sanitize-html": "^1.18.4",
     "text-encoding-utf-8": "^1.0.1",
@@ -126,6 +127,7 @@
     "@types/qrcode": "^1.3.4",
     "@types/react": "^16.9",
     "@types/react-dom": "^16.9.8",
+    "@types/react-transition-group": "^4.4.0",
     "@types/zxcvbn": "^4.4.0",
     "babel-eslint": "^10.0.3",
     "babel-jest": "^24.9.0",