Minimal code to run instant in your app:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<script src="https://dexkit-storage.nyc3.digitaloceanspaces.com/zrx/v4/instant.js"></script>
</head>
<body>
<script type="text/javascript">
function renderZeroExInstant() {
zeroExInstant.render({}, "body");
}
</script>
<button onClick="renderZeroExInstant()">Hello World</button>
</body>
</html>
The package is available as a UMD module named zeroExInstant
at https://instant.0x.org/v4/instant.js or https://dexkit-storage.nyc3.digitaloceanspaces.com/zrx/v4/instant.js.
Check 0x instant code source at Instant