Add 'detached' option

Add option 'detached' to allow the opened app to continue running after the
parent process exits.

in Linux and MacOS if this option is true, the child process `stdio` is
set to 'ignore'.

index.js

@@ -13,6 +13,7 @@ module.exports = (target, opts) => {
 	let appArgs = [];
 	let args = [];
 	const cpOpts = {};
+	cpOpts.detached = opts.detached;
 
 	if (Array.isArray(opts.app)) {
 		appArgs = opts.app.slice(1);
@@ -29,6 +30,10 @@ module.exports = (target, opts) => {
 		if (opts.app) {
 			args.push('-a', opts.app);
 		}
+
+		if (opts.detached) {
+			cpOpts.stdio = 'ignore';
+		}
 	} else if (process.platform === 'win32') {
 		cmd = 'cmd';
 		args.push('/c', 'start', '""');
@@ -56,7 +61,7 @@ module.exports = (target, opts) => {
 			args = args.concat(appArgs);
 		}
 
-		if (!opts.wait) {
+		if (!opts.wait || opts.detached) {
 			// `xdg-open` will block the process unless
 			// stdio is ignored even if it's unref'd
 			cpOpts.stdio = 'ignore';

readme.md

@@ -77,6 +77,11 @@ Specify the app to open the `target` with, or an array with the app and app argu
 
 The app name is platform dependent. Don't hard code it in reusable modules. For example, Chrome is `google chrome` on macOS, `google-chrome` on Linux and `chrome` on Windows.
 
+##### detached
+
+Type: `boolean`<br>
+
+Detachs the opened app from its node.js parent process and ignores parent `stdio` file descriptors so that it may continue to run after the parent exits.
 
 ## Related