Add TypeScript definition (#12)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

index.d.ts

@@ -0,0 +1,60 @@
+import {BrowserWindow} from 'electron';
+
+declare namespace electronServe {
+	interface Options {
+		/**
+		The directory to serve, relative to the app root directory.
+		*/
+		directory: string;
+
+		/**
+		Custom scheme. For example, `foo` results in your `directory` being available at `foo://-`.
+
+		@default 'app'
+		*/
+		scheme?: string;
+
+		/**
+		The partition the protocol should be installed to, if you're not using Electron's default partition.
+
+		@default electron.session.defaultSession
+		*/
+		partition?:string
+	}
+
+	interface loadURL {
+		/**
+		Load the index file in the window.
+		*/
+		(window: BrowserWindow): Promise<void>;
+	}
+}
+
+/**
+Static file serving for Electron apps.
+
+@example
+```
+import {app, BrowserWindow} from 'electron';
+import serve = require('electron-serve');
+
+const loadURL = serve({directory: 'renderer'});
+
+let mainWindow;
+
+(async () => {
+	await app.whenReady();
+
+	mainWindow = new BrowserWindow();
+
+	await loadURL(mainWindow);
+
+	// The above is equivalent to this:
+	await mainWindow.loadURL('app://-');
+	// The `-` is just the required hostname.
+})();
+```
+*/
+declare function electronServe(options: electronServe.Options): electronServe.loadURL;
+
+export = electronServe;

index.test-d.ts

@@ -0,0 +1,8 @@
+import {expectType} from 'tsd-check';
+import {BrowserWindow} from 'electron';
+import serve = require('.');
+
+expectType<serve.loadURL>(serve({directory: ''}));
+
+const loadURL = serve({directory: ''});
+expectType<Promise<void>>(loadURL(new BrowserWindow()));

package.json

@@ -10,10 +10,11 @@
 		"url": "sindresorhus.com"
 	},
 	"scripts": {
-		"test": "xo && cd test && ava"
+		"test": "xo && cd test && ava && tsd"
 	},
 	"files": [
-		"index.js"
+		"index.js",
+		"index.d.ts"
 	],
 	"keywords": [
 		"electron",
@@ -38,6 +39,7 @@
 		"ava": "^1.4.1",
 		"electron": "^3.0.0",
 		"spectron": "^5.0.0",
+		"tsd": "^0.7.3",
 		"xo": "^0.24.0"
 	},
 	"xo": {