Adjust DataTable types.

- Make key in `cell` slot prop less strict to prevent type errors in markup.
- Resolve property path names up to one level deep for header keys.

COMPONENT_INDEX.md

@@ -926,7 +926,8 @@ None.
 ### Types
 
 ```ts
-export type DataTableKey<Row = DataTableRow> = Exclude<keyof Row, "id">;
+export type DataTableKey<Row = DataTableRow> =
+  import("./DataTableTypes.d.ts").PropertyPath<Row>;
 
 export type DataTableValue = any;
 
@@ -962,7 +963,7 @@ export interface DataTableRow {
 export type DataTableRowId = any;
 
 export interface DataTableCell<Row = DataTableRow> {
-  key: DataTableKey<Row>;
+  key: DataTableKey<Row> | (string & {});
   value: DataTableValue;
   display?: (item: Value, row: DataTableRow) => DataTableValue;
 }