Fix various axe failures on custom EuiTable example

- missing labels on checkbox elements, duplicate checkbox ID (solved in elastic#5237)

- These are all a11y solutions that come OOTB in EuiBasicTable, but need to be added for the custom example

src-docs/src/views/tables/custom/custom.js

@@ -440,8 +440,10 @@ export default class extends Component {
  renderSelectAll = (mobile) => {
  return (
  <EuiCheckbox
- id="selectAllCheckbox"
- label={mobile ? 'Select all' : null}
+ id={mobile ? 'selectAllCheckboxMobile' : 'selectAllCheckboxDesktop'}
+ label={mobile ? 'Select all rows' : null}
+ aria-label="Select all rows"
+ title="Select all rows"
  checked={this.areAllItemsSelected()}
  onChange={this.toggleAll.bind(this)}
  type={mobile ? null : 'inList'}
@@ -522,6 +524,8 @@ export default class extends Component {
  checked={this.isItemSelected(item.id)}
  onChange={this.toggleItem.bind(this, item.id)}
  type="inList"
+ title="Select this row"
+ aria-label="Select this row"
  />
  </EuiTableRowCellCheckbox>
  );