Exit ledger-worker process on quit signal

ledger-worker.js

@@ -9,5 +9,8 @@ setInterval(()=>{
   })
 }, connected ? 5000:1000)
 
-
-
+process.on('message', function (message) {
+  if (message.quit) {
+    process.exit()
+  }
+})

main.js

@@ -186,6 +186,9 @@ function createWindow () {
     // Dereference the window object, usually you would store windows
     // in an array if your app supports multi windows, this is the time
     // when you should delete the corresponding element.
+    if (ledgerWorker.connected) {
+      ledgerWorker.send({quit: true})
+    }
     mainWindow = null
   })