Add update menu item

lib/main-app.js

@@ -121,4 +121,7 @@ app.on('ready', function() {
   ipcServer.server.start()
 })
 
-module.exports = app
+module.exports = {
+  app,
+  checkUpdate
+}

lib/main-menu.js

@@ -3,6 +3,7 @@ const BrowserWindow = electron.BrowserWindow
 const shell = electron.shell
 const ipc = electron.ipcMain
 const mainWindow = require('./main-window')
+const { checkUpdate } = require('./main-app')
 const os = require('os')
 
 const macOS = process.platform === 'darwin'
@@ -178,6 +179,18 @@ const file = {
         mainWindow.webContents.send('list:isMarkdownNote', 'print')
         mainWindow.webContents.send('print')
       }
+    },
+    {
+      type: 'separator'
+    },
+    {
+      label: 'Update',
+      click() {
+        checkUpdate()
+      }
+    },
+    {
+      type: 'separator'
     }
   ]
 }