feat: Guide for Nutri-Score V2

[g123k]

Hi everyone!

Here is the first PR to include the guide to explain the Nutri-Score V2.
This first PR only injects the content: the screen is not accessible by any means.

A few things to know:

• All translations are fetched directly from Crowdin (intl is limited to 1 file as of now)
• This screen is temporary and will be replaced later by a call to a Wordpress

Screenshot:

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 18 lines in your changes are missing coverage. Please review.

Project coverage is 8.49%. Comparing base (4d9c7fc) to head (251a5e3).
Report is 125 commits behind head on develop.

Files	Patch %	Lines
...ackages/smooth_app/lib/helpers/strings_helper.dart	0.00%	18 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #5273      +/-   ##
==========================================
- Coverage     9.54%   8.49%   -1.06%     
==========================================
  Files          325     335      +10     
  Lines        16411   17002     +591     
==========================================
- Hits          1567    1444     -123     
- Misses       14844   15558     +714     

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[teolemon]

Approved We'll have to get second opinions on the content itself