Sanitize markdown HTML output with DOMPurify to prevent XSS (#658)

package.json

@@ -58,6 +58,7 @@
     "express-slow-down": "^2.0.1",
     "got": "^11.8.6",
     "inquirer": "^8.2.6",
+    "isomorphic-dompurify": "^3.8.0",
     "istextorbinary": "^9.5.0",
     "marked": "^5.1.2",
     "mime-types": "^2.1.35",
@@ -86,6 +87,7 @@
     "@types/passport": "^1.0.16",
     "@types/passport-github2": "^1.2.9",
     "@types/unzip-stream": "^0.3.4",
+    "chai": "^4.5.0",
     "gulp": "^5.0.0",
     "gulp-clean-css": "^4.3.0",
     "gulp-concat": "^2.6.1",