refactor(pwa): revert to JS and Liquid mixing

The gem package won't be able to pass `/sw.min.js` to the user end

_javascript/pwa/app.js

@@ -1,58 +0,0 @@
-/* PWA loader */
-
-if ('serviceWorker' in navigator) {
-  const meta = document.querySelector('meta[name="pwa-cache"]');
-  const isEnabled = meta.content === 'true';
-
-  if (isEnabled) {
-    let swUrl = '/sw.min.js';
-    const baseUrl = meta.getAttribute('data-baseurl');
-
-    if (baseUrl !== null) {
-      swUrl = `${baseUrl}${swUrl}?baseurl=${encodeURIComponent(baseUrl)}`;
-    }
-
-    const $notification = $('#notification');
-    const $btnRefresh = $('#notification .toast-body>button');
-
-    navigator.serviceWorker.register(swUrl).then((registration) => {
-      // In case the user ignores the notification
-      if (registration.waiting) {
-        $notification.toast('show');
-      }
-
-      registration.addEventListener('updatefound', () => {
-        registration.installing.addEventListener('statechange', () => {
-          if (registration.waiting) {
-            if (navigator.serviceWorker.controller) {
-              $notification.toast('show');
-            }
-          }
-        });
-      });
-
-      $btnRefresh.on('click', () => {
-        if (registration.waiting) {
-          registration.waiting.postMessage('SKIP_WAITING');
-        }
-        $notification.toast('hide');
-      });
-    });
-
-    let refreshing = false;
-
-    // Detect controller change and refresh all the opened tabs
-    navigator.serviceWorker.addEventListener('controllerchange', () => {
-      if (!refreshing) {
-        window.location.reload();
-        refreshing = true;
-      }
-    });
-  } else {
-    navigator.serviceWorker.getRegistrations().then(function (registrations) {
-      for (let registration of registrations) {
-        registration.unregister();
-      }
-    });
-  }
-}