doc: optional addColumnFilters render

Author: bryanmylee

docs/src/routes/docs/[...3]plugins/[...3]add-column-filters/+page.md

@@ -51,7 +51,7 @@ Defines the filter behavior for the column.
 
 Receives `filterValue` and the column cell `value`, and returns `true` if the cell should be visible.
 
-### `render: (renderProps) => RenderConfig`
+### `render?: (renderProps) => RenderConfig`
 
 Defines the component to render on `HeaderCell->props.[pluginName].render`.