Add web front-end and fix API issues

node_modules/rxjs/dist/esm5/internal/observable/concat.js

@@ -0,0 +1,11 @@
+import { concatAll } from '../operators/concatAll';
+import { popScheduler } from '../util/args';
+import { from } from './from';
+export function concat() {
+    var args = [];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        args[_i] = arguments[_i];
+    }
+    return concatAll()(from(args, popScheduler(args)));
+}
+//# sourceMappingURL=concat.js.map