The new editor of https://github.com/odoo/odoo/pull/29775

 came with a
fullscreen option. When using the toggle when the editor is in inside
a modal, the editor stretched only to match the size of the modal
instead of the viewport.

This is because the 'position: fixed' rule which is used to achieve the
fullscreen layout cannot work if a parent of the element has a CSS
transform applied on it. Indeed in that case, that element acts like the
viewport for 'position: fixed' elements.

closes odoo/odoo#34272

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>