Improvements on Tutorial flow

[amatissart]

Some ideas suggested during a quick discussion about the tutorial:

• [x] Add more context about Tournesol and how comparisons are used in the first step of the tutorial
  • see #1110
• [ ] Allow access to Tutorial for users who already compared more than 4 users
• [x] Add a button to skip the tutorial
  • see #1470

[GresilleSiffle]

I think the replay tutorial feature should be implemented before the skip button.

If user skip the tutorial and has no way to replay it, they will lose a lot of helpful information.

[GresilleSiffle]

Allow access to Tutorial for users who already compared more than 4 users

Consider using Redux to manage this global state. The related slice could also include the "skip" state introduced by https://github.com/tournesol-app/tournesol/pull/1470

Proposition:

(1) store the setting comparison_series__skipped in an offline key of the current userSettings Redux slice. Contrary to the key settings, the key offline will contain settings that are not stored in the back end.

(2) store the settings comparison_series__skipped in the back end, with all other user settings. It will be a generic poll setting that contains a list of all comparison series that have been skipped. Then use this setting in the comparison series.

Example:

comparison_series__skipped: ["tutorial", "best_of_2022", "etc."]

I vote for the proposition (2), as I don't have use case in mind that would benefit from an "offline" setting.