Init AppImage support

ts/util/relaunch.main.ts

@@ -0,0 +1,21 @@
+// Copyright 2025 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { app } from 'electron';
+import type { RelaunchOptions } from 'electron';
+
+import OS from './os/osMain.node.js';
+
+// app.relaunch() doesn't work in AppImage, so this is a workaround
+export function appRelaunch(): void {
+  if (!OS.isAppImage()) {
+    app.relaunch();
+    return;
+  }
+
+  const options: RelaunchOptions = {
+    args: ['--appimage-extract-and-run', ...process.argv],
+    execPath: process.env.APPIMAGE,
+  };
+  app.relaunch(options);
+}