refactor: add custom tooltips

src/scss/style.scss

@@ -4,9 +4,11 @@
 $enable-ltr: true;
 $enable-rtl: true;
 
-// Import styles
+// Import CoreUI for React components library
 @import "@coreui/coreui/scss/coreui";
-@import "@coreui/chartjs/dist/css/coreui-chartjs.css";
+
+// Import Chart.js custom tooltips styles
+@import "@coreui/chartjs/scss/coreui-chartjs";
 
 @import "layout";
 @import "example";