Upgrade to NodeJS 16.13

Node 16 is the current LTS release and has support for M1 macs.
Fortunately most of our JS is very common/simple, so the upgrade should
be painless.

Making this upgrade also required replacing node-sass with sass:
facebook/create-react-app#11037
Ex. vitessio/vitess#9136

.nvmrc

@@ -1 +1 @@
-12.20
+16.13.0

package.json

@@ -5,13 +5,13 @@
   "dependencies": {
     "bootstrap": "^4.4.1",
     "font-awesome": "^4.7.0",
-    "node-sass": "^4.13.0",
     "react": "^16.12.0",
     "react-bootstrap": "^1.0.0-beta.16",
     "react-dom": "^16.12.0",
     "react-id-swiper": "^4.0.0",
     "react-router-dom": "^5.1.2",
     "react-scripts": "4.0.3",
+    "sass": "^1.43.4",
     "swiper": "^6.4.10"
   },
   "scripts": {