chore: add type definitions

Author: Noah Hummel

index.d.ts

@@ -0,0 +1,32 @@
+declare namespace dependencyTree {
+  interface TreeInnerNode {
+    [parent: string]: TreeInnerNode | string;
+  }
+  type Tree = TreeInnerNode | string;
+
+  interface Options {
+    filename: string;
+    directory: string;
+    visited?: Tree;
+    nonExistent?: string[];
+    isListForm?: boolean;
+    requireConfig?: string;
+    webpackConfig?: string;
+    nodeModulesConfig?: any;
+    detectiveConfig?: any;
+    tsConfig?: string | Record<string, any>;
+    noTypeDefinitions?: boolean;
+    filter?: (path: string) => boolean;
+  }
+
+  interface Config extends Options {
+    clone: () => Config;
+  }
+
+  function toList (options: Options): string[];
+  function _getDependencies (config: Config): string[];
+}
+
+declare function dependencyTree (options: dependencyTree.Options): dependencyTree.Tree;
+
+export = dependencyTree;

package.json

@@ -3,6 +3,7 @@
   "version": "8.0.0",
   "description": "Get the dependency tree of a module",
   "main": "index.js",
+  "types": "index.d.ts",
   "scripts": {
     "test": "jscs index.js test/test.js && ./node_modules/.bin/mocha --require esm test/test.js"
   },