Enable screen resizing

Main.go

@@ -117,6 +117,7 @@ func drawMonth(m time.Month, x, y int) {
 }
 
 func drawWall() {
+	wall.Clear()
 	w, h := wall.Size()
 	if w < monthWidth + 2 * smallGap || h < monthHeight + 2 * smallGap + titleHeight {
 		wrappedText("Екран је премали за календар.", wall, defStyle)
@@ -174,6 +175,7 @@ func main() {
 		// Process event
 		switch ev := ev.(type) {
 		case *tcell.EventResize:
+			drawWall()
 			wall.Sync()
 		case *tcell.EventKey:
 			if ev.Key() == tcell.KeyEscape || ev.Key() == tcell.KeyCtrlC ||