How to use mailto:
protocol to attache a file
https://codepen.io/Su1312/pen/bGEQgKv
function sendMail() {
var link = "mailto:me@example.com"
+ "?cc=myCCaddress@example.com"
+ "&subject=" + escape("This is my subject")
+ "&body=" + escape(document.getElementById('myText').value)
;
window.location.href = link;
}