chore: bump dompurify from 2.5.0 to 3.1.0

Bumps [dompurify](https://github.com/cure53/DOMPurify) from 2.5.0 to 3.1.0.
- [Release notes](https://github.com/cure53/DOMPurify/releases)
- [Commits](cure53/DOMPurify@2.5.0...3.1.0)

---
updated-dependencies:
- dependency-name: dompurify
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

package.json

@@ -26,7 +26,7 @@
     "connect-flash": "^0.1.1",
     "connect-mongo": "^3.0.0",
     "cookie-parser": "^1.4.3",
-    "dompurify": "^2.0.0",
+    "dompurify": "^3.1.0",
     "dotenv": "^8.0.0",
     "es6-promisify": "^6.0.0",
     "express": "^4.15.2",