[FIX] website: fix animations on rtl pages

Steps to reproduce the issue:

- Open a website page in edit mode.
- Drag and drop several snippets onto the page.
- Add a 'Fade In Right' animation to an element on the page.
- Exit edit mode.
- Change the website language to Arabic to display the scrollbar on the
left.
- Test the animation.
- Bug: the scrolling (using the mouse wheel) becomes stuck or very slow
during the animation.

The issue only occurs with Chrome or Edge browsers and seems to be a
browser display issue. It happens only when animated elements overflow
to the left.

This commit fixes the problem by adding an 'overflow: hidden' to the
main element during RTL page animations. This is not the best solution
because the animated elements become non-visible outside the main
element, creating a difference, for example, with the 'Framed' page
layout.

opw-3260399

closes odoo/odoo#118892

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