Using a new function to retrieve CSS values from classes

- create a new function to access CSS values, even if not directly used on the page;
- remove the empty harcoded HTML `<span>` placeholders used only to source the colors from CSS classes

Signed-off-by: RD WebDesign <github@rdwebdesign.com.br>

scripts/pi-hole/js/utils.js

@@ -408,6 +408,13 @@ function changeBulkDeleteStates(table) {
   }
 }
 
+function getCSSval(cssclass, cssproperty) {
+  var elem = $("<div class='" + cssclass + "'></div>"),
+    val = elem.appendTo("body").css(cssproperty);
+  elem.remove();
+  return val;
+}
+
 window.utils = (function () {
   return {
     escapeHtml: escapeHtml,
@@ -432,5 +439,6 @@ window.utils = (function () {
     colorBar: colorBar,
     checkMessages: checkMessages,
     changeBulkDeleteStates: changeBulkDeleteStates,
+    getCSSval: getCSSval,
   };
 })();