Add PWA support (I think)

static/manifest.json

@@ -0,0 +1,12 @@
+{
+  "name": "ReSendit",
+  "short_name": "ReSendit",
+  "start_url": "/",
+  "display": "standalone",
+  "background_color": "#ffffff",
+  "theme_color": "#000000",
+  "icons": [
+    { "src": "/logo.png", "sizes": "192x192", "type": "image/png" },
+    { "src": "/logo.png", "sizes": "512x512", "type": "image/png" }
+  ]
+}

static/sw.js

@@ -0,0 +1,13 @@
+self.addEventListener('install', e => {
+    e.waitUntil(
+        caches.open('resendit-v1').then(cache => {
+            return cache.addAll(['/', '/index.html', '/login.html', '/logo.png']);
+        })
+    );
+});
+
+self.addEventListener('fetch', e => {
+    e.respondWith(
+        caches.match(e.request).then(response => response || fetch(e.request))
+    );
+});

templates/index.html

@@ -6,6 +6,12 @@
     <title>Send.it</title>
     <script src="https://cdn.tailwindcss.com"></script>
     <link rel="icon" type="image/x-icon" href="/static/favicon.ico">
+    <link rel="manifest" href="/manifest.json">
+    <script>
+        if ('serviceWorker' in navigator) {
+            navigator.serviceWorker.register('/sw.js');
+        }
+    </script>
     <style>
         * {
             border-radius: 0 !important;