Add web front-end and fix API issues

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

@@ -0,0 +1,11 @@
+import { EmptyError } from '../util/EmptyError';
+import { filter } from './filter';
+import { take } from './take';
+import { defaultIfEmpty } from './defaultIfEmpty';
+import { throwIfEmpty } from './throwIfEmpty';
+import { identity } from '../util/identity';
+export function first(predicate, defaultValue) {
+    const hasDefaultValue = arguments.length >= 2;
+    return (source) => source.pipe(predicate ? filter((v, i) => predicate(v, i, source)) : identity, take(1), hasDefaultValue ? defaultIfEmpty(defaultValue) : throwIfEmpty(() => new EmptyError()));
+}
+//# sourceMappingURL=first.js.map