add custom-electron-prompt

also use it to set proxy option

plugins/in-app-menu/prompt-custom-titlebar.js

@@ -0,0 +1,14 @@
+const customTitlebar = require("custom-electron-titlebar");
+
+module.exports = () => {
+	const bar = new customTitlebar.Titlebar({
+		backgroundColor: customTitlebar.Color.fromHex("#050505"),
+		minimizable: false,
+		maximizable: false,
+		menu: null
+	});
+	const mainStyle = document.querySelector("#container").style;
+	mainStyle.width = "100%";
+	mainStyle.position = "fixed";
+	mainStyle.border = "unset";
+};