Allow users to use stacked line charts. The chart.js configuration
is mimicking the one inside Odoo community.
task 2888350
closesodoo/odoo#102312
X-original-commit: 1ccb2cd685c60eecd767eb15967d4b4c25262ded
Related: odoo/enterprise#32345
Signed-off-by: Lucas Lefèvre (lul) <lul@odoo.com>
Signed-off-by: Rémi Rahir (rar) <rar@odoo.com>