Table: Add filter-placement for table filter Popper; If the column is too wide, the popper's position will be improper;

https://jsfiddle.net/whitewang/obpsLcva/7/

packages/table/src/table-header.js

@@ -256,7 +256,7 @@ export default {
         filterPanel = new Vue(FilterPanel);
         this.filterPanels[column.id] = filterPanel;
         if (column.filterPlacement) {
-            filterPanel.placement = column.filterPlacement;
+          filterPanel.placement = column.filterPlacement;
         }
         filterPanel.table = table;
         filterPanel.cell = cell;