Keep UTM parameters for Unbounce

I have used Unbounce to quickly set up A/B tests and find out which landing page converts better.
The funnel is always like this:
1) Facebook Ad
2) Unbounce landing page
3) Check out Shopify/Woocommerce.

The problem is that I lose the UTM parameters when people click on the Buy button on the Unbounce landing page. This is because the Unbounce landing page doesn't transfer the UTM parameters.

With this script, the UTM parameters are transferred to the links in the Unbounce landing page.