Update moment dependency to fix potential security vulnerability (as suggested by github)

package.json

@@ -36,7 +36,7 @@
     "history": "4.7.2",
     "live-server": "1.2.0",
     "marked": "0.3.9",
-    "moment": "2.19.3",
+    "moment": "2.22.1",
     "postcss-cli": "4.1.1",
     "postcss-css-variables": "0.8.0",
     "postcss-custom-media": "^6.0.0",

yarn.lock

@@ -2513,9 +2513,9 @@ minimist@^1.2.0:
   dependencies:
     minimist "0.0.8"
 
-moment@2.19.3:
-  version "2.19.3"
-  resolved "https://registry.yarnpkg.com/moment/-/moment-2.19.3.tgz#bdb99d270d6d7fda78cc0fbace855e27fe7da69f"
+moment@2.22.1:
+  version "2.22.1"
+  resolved "https://registry.yarnpkg.com/moment/-/moment-2.22.1.tgz#529a2e9bf973f259c9643d237fda84de3a26e8ad"
 
 morgan@^1.6.1:
   version "1.8.1"