boast-form:loaded and boast-form:submitted are two events that are triggered via JavaScript. You can listen for those events using code like this:

<script>
      document.addEventListener("boast-form:loaded", function(e) {
        console.log("host page heard event", "boast-form:loaded", e)
      });
      document.addEventListener("boast-form:submitted", function(e) {
        console.log("host page heard event", "boast-form:submitted", e)
      });      
</script>