Replacing global themed sass-vars to css-vars (#4322)

* generating css-vars
* convert all global / theme sass vars to css vars with available default theme colors
* added missing colors to dark lens theme

src/renderer/port-forward/port-forward-dialog.scss

@@ -56,7 +56,7 @@
     }
 
     .warning {
-      color: $colorSoftError;
+      color: var(--colorSoftError);
       font-size: small;
       display: flex;
       align-items: center;