fix(testWithSpectron): making options param optional, has default (#196)

Author: jaredmcateer

index.d.ts

@@ -31,4 +31,4 @@ interface Server {
    Run electron:serve, but instead of launching Electron it returns a Spectron Application instance.
    Used for e2e testing with Spectron.
 */
-export function testWithSpectron(options: Options): Promise<Server>
+export function testWithSpectron(options?: Options): Promise<Server>