[FIX] website_slides: prevent content title overflow

This commit resolves the issue of content title overflow in both fullscreen
and non-fullscreen views by cropping the title and adding '...' at the end.

Task-3384661

closes odoo/odoo#136607

X-original-commit: b13da52bffaa91b9a63d386ba317acccab40c565
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>