Bump @types/node from 12.0.8 to 12.6.8 in /app (#167)

Bumps [@types/node](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/node) from 12.0.8 to 12.6.8.
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/node)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

app/package.json

@@ -57,7 +57,7 @@
     "@types/d3": "^5.7.2",
     "@types/diff": "^4.0.1",
     "@types/get-value": "^3.0.1",
-    "@types/node": "^12.0.4",
+    "@types/node": "^12.6.8",
     "@types/prismjs": "^1.9.1",
     "@types/react": "^16.8.23",
     "@types/react-dom": "^16.0.11",