add isIosSafari and isSafariBrowser functions

These helper functions will be used in a follow up commit

src/page/utils/BrowserSupportsPush.ts

@@ -11,7 +11,7 @@ export function isMacOSSafariInIframe(): boolean {
   // Fallback detection for Safari on macOS in an iframe context
   return (
     window.top !== window && // isContextIframe
-    navigator.vendor === 'Apple Computer, Inc.' && // isSafari
+    isSafariBrowser() &&
     navigator.platform === 'MacIntel'
   ); // isMacOS
 }
@@ -32,6 +32,19 @@ export function supportsVapidPush(): boolean {
   );
 }
 
+// Is Safari on iOS or iPadOS
+export function isIosSafari(): boolean {
+  // Safari's "Request Desktop Website" (default for iPad) masks the
+  // userAgent as macOS. So we are using maxTouchPoints to assume it is
+  // iOS, since there are no touch screen Macs.
+  return isSafariBrowser() && navigator.maxTouchPoints > 0;
+}
+
+// Is any Safari browser, includes macOS and iOS.
+function isSafariBrowser(): boolean {
+  return navigator.vendor === 'Apple Computer, Inc.';
+}
+
 /* Notes on browser results which lead the logic of the functions above */
 // Safari
 //   macOS - typeof safari.pushNotification == "object"