Add Application.RingBell

CHANGELOG

@@ -1,5 +1,6 @@
 v1.4.1 (WIP)
 - Add ProgressBar widget
+- Add Application.RingBell
 
 v1.4.0 (2020-01-16)
 - Bump version to resolve issues with "go get"

application.go

@@ -1,6 +1,7 @@
 package cview
 
 import (
+	"fmt"
 	"sync"
 	"time"
 
@@ -745,3 +746,10 @@ func (a *Application) QueueEvent(event tcell.Event) *Application {
 	a.events <- event
 	return a
 }
+
+// RingBell sends a bell code to the terminal.
+func (a *Application) RingBell() {
+	a.Lock()
+	fmt.Print(string(byte(7)))
+	a.Unlock()
+}