[promise-limit_v2.x.x] Add libdefs for promise-limit (#3044)

* Add types for promise-limit

* Add type assertion

* Wrap tests in describe/it, as suggested

definitions/npm/promise-limit_v2.x.x/flow_v0.25.x-/promise-limit_v2.x.x.js

@@ -0,0 +1,21 @@
+/**
+ * Flow libdef for 'promise-limit'
+ * See https://www.npmjs.com/package/promise-limit
+ * by Vincent Driessen, 2019-01-04
+ */
+
+declare module 'promise-limit' {
+  declare type limit<T> = limitFunc<T> & limitInterface<T>;
+  declare type limitFunc<T> = (fn: () => Promise<T>) => Promise<T>;
+  declare interface limitInterface<T> {
+    map<U>(
+      items: $ReadOnlyArray<T>,
+      mapper: (value: T) => Promise<U>,
+    ): Promise<Array<U>>;
+    queue: number;
+  }
+
+  declare export default function limitFactory<T>(
+    concurrency?: number,
+  ): limit<T>;
+}

definitions/npm/promise-limit_v2.x.x/test_promise-limit_v2.x.x.js

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+// @flow strict
+
+import { describe, it } from "flow-typed-test";
+import limit from "promise-limit";
+
+describe("promise-limit", () => {
+  it("errors", () => {
+    // $ExpectError
+    limit("");
+  });
+
+  it("works", () => {
+    const limiter = limit(3);
+
+    function dosomething_(): Promise<string> {
+      return Promise.resolve("hi");
+    }
+    const dosomething = () => limiter(() => dosomething_());
+    (dosomething: () => Promise<string>);
+  });
+});