Add web front-end and fix API issues

node_modules/rxjs/dist/esm/internal/operators/concat.js

@@ -0,0 +1,11 @@
+import { operate } from '../util/lift';
+import { concatAll } from './concatAll';
+import { popScheduler } from '../util/args';
+import { from } from '../observable/from';
+export function concat(...args) {
+    const scheduler = popScheduler(args);
+    return operate((source, subscriber) => {
+        concatAll()(from([source, ...args], scheduler)).subscribe(subscriber);
+    });
+}
+//# sourceMappingURL=concat.js.map