(Signing + Drawing) in one file, in one javascript library - for quick and easy use.
Create a .html file, with all the your markup. Then, include the Drawer.js file, which you can download and serve yourself:
<!DOCTYPE html>
<html>
<head>
<title>Some webpage on the internet</title>
<!-- .... (some other content you include) ... -->
</head>
<body>
<canvas id="pad"></canvas>
<script src="./Drawer.js"></script>
<script>
var canvas = document.getElementById("pad");
var drawer = new Drawer(canvas);
// you can now sign + draw on the canvas
</script>
</body>
</html>