Add web front-end and fix API issues

node_modules/rxjs/dist/esm/internal/util/EmptyError.js

@@ -0,0 +1,7 @@
+import { createErrorClass } from './createErrorClass';
+export const EmptyError = createErrorClass((_super) => function EmptyErrorImpl() {
+    _super(this);
+    this.name = 'EmptyError';
+    this.message = 'no elements in sequence';
+});
+//# sourceMappingURL=EmptyError.js.map