add single instance lock option

index.js

@@ -26,6 +26,22 @@ unhandled({
 process.env.NODE_OPTIONS = "";
 
 const app = electron.app;
+// Prevent window being garbage collected
+let mainWindow;
+autoUpdater.autoDownload = false;
+
+if(config.get("options.singleInstanceLock")){
+	const gotTheLock = app.requestSingleInstanceLock();
+	if (!gotTheLock) app.quit();
+
+	app.on('second-instance', () => {
+		if (!mainWindow) return;
+		if (mainWindow.isMinimized()) mainWindow.restore();
+		if (!mainWindow.isVisible()) mainWindow.show();
+		mainWindow.focus();
+	});
+}
+
 app.commandLine.appendSwitch(
 	"js-flags",
 	// WebAssembly flags
@@ -54,10 +70,6 @@ require("electron-debug")({
 	showDevTools: false //disable automatic devTools on new window
 });
 
-// Prevent window being garbage collected
-let mainWindow;
-autoUpdater.autoDownload = false;
-
 let icon = "assets/youtube-music.png";
 if (process.platform == "win32") {
 	icon = "assets/generated/icon.ico";

menu.js

@@ -87,6 +87,19 @@ const mainMenuTemplate = (win) => {
 						config.set("options.removeUpgradeButton", item.checked);
 					},
 				},
+				{
+					label: "Single instance lock",
+					type: "checkbox",
+					checked: config.get("options.singleInstanceLock"),
+					click: (item) => {
+						config.set("options.singleInstanceLock", item.checked);
+						if (item.checked && !app.hasSingleInstanceLock()) {
+							app.requestSingleInstanceLock();
+						} else if (!item.checked && app.hasSingleInstanceLock()) {
+							app.releaseSingleInstanceLock();
+						}
+					},
+				},
 				...(is.windows() || is.linux()
 					? [
 						{