chore(eui): add JSDoc to EuiInMemoryTable message prop

Author: weronikaolejniczak

packages/eui/src/components/basic_table/in_memory_table.tsx

@@ -75,6 +75,9 @@ type InMemoryTableProps<T extends object> = Omit<
   EuiBasicTableProps<T>,
   'pagination' | 'sorting' | 'noItemsMessage' | 'onChange'
 > & {
+  /**
+   * Message to display if table is empty
+   */
   message?: ReactNode;
   /**
    * Configures {@link Search}.