[IMP] web_editor: add touchscreen support for the editor

Before this commit, website and email editing was very limited on
devices that have a touchscreen. The blocks tab, the we-lists, ... were
unusable.
Example of issues (on a device that has a touchscreen):
- The users cannot drag & drop snippets in the page.
- The users cannot reorder the values of a multiple checkboxes field.
- ...

This commit allows to handle touchscreen events by translating them
into mouse events to allow users to fully use the editor.

opw-3195487

closes odoo/odoo#114485

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