Migrate to ESM and fix window sizing on Windows

index.js

@@ -1,4 +1,17 @@
-const { app, BrowserWindow } = require('electron');
+import { app, BrowserWindow } from 'electron';
+
+// A helper function for creating the window
+const createWindow = () => {
+    const win = new BrowserWindow({
+        width: 290,
+        height: 465,
+        resizable: false,
+        autoHideMenuBar: true,
+        useContentSize: true,
+    });
+
+    win.loadFile('static/index.html');
+};
 
 app.whenReady().then(() => {
     createWindow();
@@ -13,15 +26,4 @@ app.whenReady().then(() => {
 // If all windows are closed and we're not running macOS, quit the app.
 app.on('window-all-closed', () => {
     if (process.platform !== 'darwin') app.quit();
-});
-
-function createWindow() {
-    const win = new BrowserWindow({
-        width: 280,
-        height: 485,
-        resizable: false,
-        autoHideMenuBar: true,
-    });
-
-    win.loadFile('static/index.html');
-}
+});

package.json

@@ -3,6 +3,7 @@
   "version": "1.0.0",
   "description": "Prosty kalkulator w Electronie",
   "main": "index.js",
+  "type": "module",
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1",
     "start": "electron ."