Add VS Code extension recommendations and settings

Author: karlhorky

.vscode/extensions.json

@@ -0,0 +1,7 @@
+{
+  "recommendations": [
+    "flowtype.flow-for-vscode",
+    "esbenp.prettier-vscode",
+    "dbaeumer.vscode-eslint"
+  ]
+}

.vscode/settings.json

@@ -6,5 +6,8 @@
     "./services/auth-server"
   ],
   "git.ignoreLimitWarning": true,
-  "javascript.validate.enable": false
+  "javascript.validate.enable": false,
+  "files.trimTrailingWhitespace": true,
+  "prettier.eslintIntegration": true,
+  "flow.useNPMPackagedFlow": true
 }