[IMP] web_gantt: add documentation
[IMP] web_gantt: add documentation

Add documentation about the new gantt parameter, `dynamic_range`,
The parameters were added in enterprise (odoo/enterprise#7640).

Task #2168740

closes odoo/odoo#43052

Related: odoo/enterprise#7640
Signed-off-by: Thibault Delavallee (tde) <2d325771bb6e8870d87f0f3f7b45589a8338e550@openerp.com>

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo