waybar: improve tooltip label contrast (#1919)

Link: https://github.com/nix-community/stylix/pull/1919

Reviewed-by: NAHO <90870942+trueNAHO@users.noreply.github.com>
Reviewed-by: awwpotato <awwpotato@voidq.com>

modules/waybar/hm.nix

@@ -111,6 +111,10 @@ mkTarget {
               tooltip {
                   border-color: @base0D;
               }
+
+              tooltip label {
+                  color: @base05;
+              }
             ''
             + (builtins.readFile ./base.css)
             + (