set up service worker caching, fix perf issues with rerenders, split code into more modules, switch to a green theme, add modal for updating site via service worker

public/manifest.json

@@ -1,21 +0,0 @@
-{
-  "name": "SURE",
-  "short_name": "SURE",
-  "theme_color": "#44a616",
-  "background_color": "#3d006e",
-  "display": "minimal-ui",
-  "scope": "/",
-  "start_url": "/",
-  "icons": [
-    {
-      "src": "/android-chrome-192x192.png",
-      "sizes": "192x192",
-      "type": "image/png"
-    },
-    {
-      "src": "/android-chrome-512x512.png",
-      "sizes": "512x512",
-      "type": "image/png"
-    }
-  ]
-}