Request ANSI colour codes when calling gravity API

Add the 'color=true' query parameter to the gravity API call so that the
FTL backend will include ANSI escape codes for terminal color output.

This works in conjunction with FTL changes that make color codes opt-in
rather than always-on.

Addresses: pi-hole/FTL#2671

Author: PromoFaux

scripts/js/gravity.js

@@ -15,7 +15,7 @@ function eventsource() {
   const outputElement = document.getElementById("output");
   const gravityBtn = document.getElementById("gravityBtn");
   const csrfToken = document.querySelector('meta[name="csrf-token"]').getAttribute("content");
-  const url = `${document.body.dataset.apiurl}/action/gravity`;
+  const url = `${document.body.dataset.apiurl}/action/gravity?color=true`;
 
   if (outputElement.innerHTML.length > 0) {
     outputElement.innerHTML = "";