add lighter override to custom.scss to take effect

resources/assets/sass/custom.scss

@@ -132,6 +132,10 @@ body, button, input, textarea {
     background-color: rgba(0,0,0,0.5);
 }
 
+.font-weight-lighter {
+    font-weight: 300 !important
+}
+
 .font-weight-ultralight {
     font-weight: 200 !important;
 }