[FIX] web_editor: mediaDialog should trigger change
[FIX] web_editor: mediaDialog should trigger change

before this event, when editing an email template from the chatter
by adding an image through the mediaDialog, the message was always empty
if nothing more than the image was present.
this was because the html field was not marked as dirty,
the event responsible for the marking was not triggered.

After this commit, when sending solely an image from the media dialog,
the email sent does contain the image

opw 779167

closes #20817

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