EditableGridCell should have a common newValue property

[dvdsgl]

type EditableGridCell = TextCell | ImageCell | BooleanCell | MarkdownCell | UriCell | NumberCell;

EditableGridCell does not have a common property across union types that represents the new value, so you have to do clumsy checking in onCellEdited (for example). It would be nice to be able to:

onCellEdited={([col, row], editedCell) => console.log(editedCell.newValue)}

[schani]

I think the naming is just bad:

• Most cells have data, except for BooleanCell, which has checked.
• Some cells also have editData, which is the actual underlying value, whereas their data is the display value.

I think we should

• Make data always be the underlying value, and have an optional displayData when appropriate.
• Rename checked in BooleanCell to data.