feat(grid): support multi-row Copy as INSERT

When multiple rows are selected, copyRowAsInsert now generates an
INSERT statement for each selected row instead of only the
right-clicked row.

Closes #166

src/components/grid/DataGrid.vue

@@ -1402,6 +1402,7 @@ const {
   databaseType: computed(() => props.databaseType),
   hasCellSelection,
   selectedCells,
+  selectedRange,
   contextCell: exportContextCell,
   getRowItem: (rowId: number) => visibleDisplayItems.value.find((item) => item.id === rowId),
   quoteIdent,