Close Burger Menu by clicking outside the box | JavaScript

Hey experts!
I need help with injecting code (Java Script) to be able to close the burger menu without clicking on the X.
The website is not public yet, so I can't share the URL, unfortunately.
Can someone still help, or should I come back once we're public?

Thanks in advance!!  Lisa 

I added  CSS to get this results so far (see photo).

/* Burger */
.header .header-burger{display:flex}
.header-nav, .header-actions {display:none}

/* Change menu size */
.header--menu-open .header-menu {
opacity: 1; visibility: visible;
     bottom:0vh; 
    left:65%!important; 
    right:-5vw; 
    top:0vh 
}
/* Change alignment & spacing */
.header-menu-nav-folder-content{
 justify-content:flex-start !important
}

.header--menu-open  .header{ 
    top:0vh; 
    left:0vw
}  
/* Burger Menu font size*/
.header-menu-nav-item a {
font-size: 110%; line-height: 60%
}

Tuan Phan answered me: 

You can use this code to Website > Website Tools > Code Injection > Footer (DO NOT add code to CUSTOM CSS)



Thank you!! 🥰