Outbound live stream notifications (#1663)

* First pass at browser, discord, twilio notifications

* Commit updated Javascript packages

* Remove twilio notification support

* Email notifications/smtp support

* Fix Firefox notification support, remove chrome checks

* WIP more email work

* Add support for twitter notifications

* Add stream title to discord and twitter notifications

* Update notification registration modal

* Fix hide/show email section

* Commit updated API documentation

* Commit updated Javascript packages

* Fix post-rebase missing var

* Remove unused var

* Handle unsubscribe errors for browser push

* Standardize email config prop names

* Allow overriding go live email template

* Some notifications cleanup

* Commit updated Javascript packages

* Remove email/smtp/mailjet support

* Remove more references to email notifications

Co-authored-by: Owncast <owncast@owncast.online>

webroot/js/notification/registerWeb.js

@@ -0,0 +1,30 @@
+export async function registerWebPushNotifications(vapidPublicKey) {
+  const registration = await navigator.serviceWorker.ready;
+  let subscription = await registration.pushManager.getSubscription();
+
+  if (!subscription) {
+    subscription = await registration.pushManager.subscribe({
+      userVisibleOnly: true,
+      applicationServerKey: urlBase64ToUint8Array(vapidPublicKey),
+    });
+  }
+
+  return JSON.stringify(subscription);
+}
+
+export function isPushNotificationSupported() {
+  return 'serviceWorker' in navigator && 'PushManager' in window;
+}
+
+function urlBase64ToUint8Array(base64String) {
+  var padding = '='.repeat((4 - (base64String.length % 4)) % 4);
+  var base64 = (base64String + padding).replace(/\-/g, '+').replace(/_/g, '/');
+
+  var rawData = window.atob(base64);
+  var outputArray = new Uint8Array(rawData.length);
+
+  for (var i = 0; i < rawData.length; ++i) {
+    outputArray[i] = rawData.charCodeAt(i);
+  }
+  return outputArray;
+}