[IMP] website_slides: Add elearning feature to slides

Purpose of this commit is to introduce a new way of displaying and managing
slides in eLearning module. Its purpose is to give a better experience to
users when going through a course. Notably a fullscreen mode allows to take
lessons one by one without going out of the elearning display. Integration
of all slide types eases taking the course step by step.

Quiz are introduced in this commit. Those are an addition to slides with
some question / answers (multiple choice). It allows customer to gain karma
and improves gamification. Certifications are still done using the survey
application. Quiz targets only small tests at the end of a given slide.

A new widget is added to display and control slide display in fullscreen
mode. Old display is still available for documentation channels or when
going out of fullscreen mode, to see details on comments / review / statistics
and have access to share options.

This commit is linked to task ID 1902304 and PR #29876. It closes the main
work on refactoring website slides into eLearning, with other tasks already
merged in current community [1][2][3][4][5].

[1] Task ID 1940360 landed at b2149bc7: certification inclusion
[2] Task ID 1936153 landed at 6c6179e5: homepage inclusion
[3] Task ID 1937160 landed at 8b7605c9: selling courses
[4] Task ID 1922159 and 1940516 landed at 5fa651cb and 6a64c3ce:
    new user profile and gamification of slides / forum
[5] Task ID 1938643 landed at 77b5673a: upload channel/slide