fix(slidepane): update icon position (#434)

Author: LuckyFBB

Diff for: src/slidePane/style.scss

@@ -77,6 +77,9 @@ $prefix: "dtc-slide-pane";
     }
     &-nested-loading {
         height: 100%;
+        .ant-spin-container {
+            height: 100%;
+        }
     }
 }