Add web front-end and fix API issues

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

@@ -0,0 +1,6 @@
+import { concat } from '../observable/concat';
+import { of } from '../observable/of';
+export function endWith(...values) {
+    return (source) => concat(source, of(...values));
+}
+//# sourceMappingURL=endWith.js.map