Images: Check image sizes, show which ones are too big

[YodaSpow]

Is your feature request related to a problem? Please describe.
Would like to check if images are too big, not the width or height but the actual KB/MB.

Describe the solution you'd like
Thinking any image which over 300KB would get flagged with a pop up.

Describe alternatives you've considered
Lists all images in an email that is too large, preferably there would be a tooltip showing

Example from Litmus Rendercheck

[YodaSpow]

Post:
http://voidcanvas.com/how-to-get-the-memory-size-byte-kb-mb-of-an-image-or-other-files-without-loading-it-by-javascriptajax/

<!DOCTYPE html>
<html>
	<head>
		<title>Get memory size of a file</title>
		<script type="text/javascript" src="main.js"></script>
	</head>
	
	<body onLoad="toGetSize()">

	</body>
</html>

function toGetSize() {

var obj = new XMLHttpRequest();
obj.open('HEAD', 'images/1.png', true);
obj.onreadystatechange = function(){
  if ( obj.readyState == 4 ) {
    if ( obj.status == 200 ) {
      alert('Size in bytes: ' + obj.getResponseHeader('Content-Length'));
    } else {
      alert('ERROR');
    }
  }
};
obj.send(null);

}

[YodaSpow]

https://www.codexworld.com/how-to/convert-file-size-bytes-kb-mb-gb-javascript/

https://www.webdeveloper.com/d/219516-how-to-get-file-size-and-file-name-of-an-image-in-domjavascript

[YodaSpow]

https://www.codexworld.com/how-to/convert-file-size-bytes-kb-mb-gb-javascript/

[YodaSpow]

Not fully related: https://stackoverflow.com/questions/934012/get-image-data-url-in-javascript/42916772#42916772
demo: canvas: http://jsfiddle.net/Parth_Raval/rqdw3s71/1/

[YodaSpow]

https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch
https://developer.mozilla.org/en-US/docs/Web/API/FileReader

[YodaSpow]

https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API
demo: https://github.com/mdn/sw-test

[YodaSpow]

https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Fetching_data