Add TypeScript types (#8)

index.d.ts

@@ -0,0 +1,31 @@
+interface Options {
+	/**
+	Milliseconds to wait before giving up.
+
+	@default 1000
+	*/
+	timeout?: number;
+
+	/**
+	Can be a domain or an IP.
+
+	@default 'localhost'
+	*/
+	host?: string;
+}
+
+/**
+Check if a local or remote port is reachable.
+
+@example
+```
+import isPortReachable from 'is-port-reachable';
+
+if(await isPortReachable(3000)) {
+	// start server
+}
+```
+*/
+declare function isPortReachable(port: number, options?: Options): Promise<boolean>;
+
+export = isPortReachable;

index.test-d.ts

@@ -0,0 +1,4 @@
+import {expectType} from 'tsd';
+import isPortReachable = require('.');
+
+expectType<boolean>(await isPortReachable(3000));

package.json

@@ -16,10 +16,11 @@
 		"node": ">=8"
 	},
 	"scripts": {
-		"test": "xo && ava"
+		"test": "xo && ava && tsd"
 	},
 	"files": [
-		"index.js"
+		"index.js",
+		"index.d.ts"
 	],
 	"keywords": [
 		"port",
@@ -40,6 +41,7 @@
 	],
 	"devDependencies": {
 		"ava": "^2.4.0",
-		"xo": "^0.25.3"
+		"xo": "^0.25.3",
+		"tsd": "^0.17.0"
 	}
 }