Fix tailwind setup

- Adopted postcss and tailwind config to new version
- renamed colors bluegray->slate etc to not have custom
  definitions (hope to reduce migration next time)
- tailwind now doesn't build the complete css anymore, so the
  `dev-ui-build` script must compile both

modules/webapp/src/main/elm/Comp/Basic.elm

@@ -178,12 +178,12 @@ linkLabel model =
             [ class S.basicLabel
             , class "inline-block md:text-sm my-auto whitespace-nowrap"
             , class "border-blue-500 text-blue-500 "
-            , class "dark:border-lightblue-300 dark:text-lightblue-300"
+            , class "dark:border-sky-300 dark:text-sky-300"
             ]
 
         hover =
             [ class "hover:bg-blue-500 hover:text-gray-200"
-            , class "dark:hover:bg-lightblue-300 dark:hover:text-bluegray-900"
+            , class "dark:hover:bg-sky-300 dark:hover:text-slate-900"
             ]
 
         attrs =