Update dependency express to v4.20.0 [SECURITY]

Author: renovate[bot]

package.json

@@ -58,7 +58,7 @@
     "d3-color": "^1.2.0",
     "d3-interpolate": "^1.2.0",
     "d3-scale": "^2.1.0",
-    "express": "4.16.3",
+    "express": "4.20.0",
     "fs-extra": "5.0.0",
     "glob-promise": "^3.4.0",
     "graphql": "^0.13.2",