Revert "refactor: Clean up golden-layout css (#1322)"

This reverts commit d1838d7.

Author: mofojed

package-lock.json

@@ -4,13 +4,9 @@
   display: flex;
   flex-direction: column;
   justify-content: center;
+  padding: $spacer-3;
   min-height: 100%;
   max-height: 100%;
   text-align: center;
   overflow: hidden;
-
-  // add padding on an inner wrapper so it is included in max height of parent
-  div {
-    padding: $spacer-3;
-  }
 }

packages/dashboard/src/PanelPlaceholder.scss

@@ -11,7 +11,7 @@ const PanelPlaceholder = React.forwardRef(
     const component = LayoutUtils.getComponentNameFromPanel({ props });
     return (
       <div ref={ref} className="panel-placeholder">
-        <div>Component &quot;{component}&quot; is not registered.</div>
+        Component &quot;{component}&quot; is not registered.
       </div>
     );
   }

packages/dashboard/src/PanelPlaceholder.tsx

@@ -0,0 +1,9 @@
+@import '@deephaven/components/scss/custom.scss';
+@import './GoldenLayout.scss';
+
+// Exported variables for use in GoldenLayoutThemeExport.js
+/* stylelint-disable property-no-unknown */
+:export {
+  tab-height: $tab-height;
+  drag-border-width: $drag-border-width;
+}