- Support extra attributes on each field cell via field_extra_attrs
  param. We could set a cell as not editable, required or readonly for
  instance. The readonly case will also give the ability to click on m2o
  to open related records.
- Support limit total records in the matrix. Ref:
  <https://github.com/OCA/web/issues/901>
- Support cell traversal through keyboard arrows.
- Entering the widget from behind by pressing `Shift+TAB` in your
  keyboard will enter into the 1st cell until
  <https://github.com/odoo/odoo/pull/26490> is merged.
- Support extra invisible fields inside each cell.
- Support kanban mode. Current behaviour forces list mode.
