Add typescript type tests for after

Author: Avaq

test/types/after.test-d.ts

@@ -0,0 +1,9 @@
+import {expectType} from 'tsd';
+
+import * as fl from '../../index.js';
+
+expectType<fl.Resolved<number>> (fl.after (1) (42));
+expectType<fl.Resolved<string>> (fl.after (1) ('a'));
+
+// https://github.com/microsoft/TypeScript/issues/32277
+// expectType<fl.Never> (fl.after (Infinity) ('Finally!'));