feat(toolbar): add column visibility and CSV export features

- Implemented GridToolbar component for column visibility and CSV export
- Added ColumnVisibilityMenu for toggling column visibility
- Created exportToCsv function for exporting visible data to CSV
- Updated Griddy component to integrate toolbar functionality
- Enhanced documentation with examples for new features

src/Griddy/features/columnVisibility/ColumnVisibilityMenu.tsx

@@ -0,0 +1,48 @@
+import type { Table } from '@tanstack/react-table'
+
+import { ActionIcon, Checkbox, Menu, Stack } from '@mantine/core'
+import { IconColumns } from '@tabler/icons-react'
+
+interface ColumnVisibilityMenuProps<T> {
+  table: Table<T>
+}
+
+export function ColumnVisibilityMenu<T>({ table }: ColumnVisibilityMenuProps<T>) {
+  const columns = table.getAllColumns().filter(col =>
+    col.id !== '_selection' && col.getCanHide()
+  )
+
+  if (columns.length === 0) {
+    return null
+  }
+
+  return (
+    <Menu position="bottom-end" shadow="md" width={200}>
+      <Menu.Target>
+        <ActionIcon aria-label="Toggle columns" size="sm" variant="subtle">
+          <IconColumns size={16} />
+        </ActionIcon>
+      </Menu.Target>
+
+      <Menu.Dropdown>
+        <Menu.Label>Toggle Columns</Menu.Label>
+        <Stack gap="xs" p="xs">
+          {columns.map(column => {
+            const header = column.columnDef.header
+            const label = typeof header === 'string' ? header : column.id
+
+            return (
+              <Checkbox
+                checked={column.getIsVisible()}
+                key={column.id}
+                label={label}
+                onChange={column.getToggleVisibilityHandler()}
+                size="xs"
+              />
+            )
+          })}
+        </Stack>
+      </Menu.Dropdown>
+    </Menu>
+  )
+}

src/Griddy/features/columnVisibility/index.ts

@@ -0,0 +1 @@
+export { ColumnVisibilityMenu } from './ColumnVisibilityMenu'