The default header menu icon is a triangle. It would be great if this could be configured by providing an arbitrary SVG.

Two potential API options:

1. Make it configurable on a per column-basis by adding a menuIcon property to GridColumn that works the same way as the icon property.
2. Add a headerMenuIcon property to the data editor that allows to configure it globally:

interface DataEditorProps {
    // ...other props
    headerMenuIcon?: Sprite;
}