fixed minor bugs in dark-theme (#523)

* fixed code copy button's color in dark mode

* Update theme-dark.scss

Author: jitendravjh

theming/theme-dark.scss

@@ -123,3 +123,9 @@ p {
     color: $links-hover;
     background: $background-nav;
 }
+
+
+.tooltip {
+    --bs-tooltip-color: $black !important;
+    --bs-tooltip-bg: $white !important;
+}