Add web front-end and fix API issues

node_modules/rxjs/dist/esm5/internal/util/isPromise.js

@@ -0,0 +1,5 @@
+import { isFunction } from "./isFunction";
+export function isPromise(value) {
+    return isFunction(value === null || value === void 0 ? void 0 : value.then);
+}
+//# sourceMappingURL=isPromise.js.map