Add a message about the benefits of the Open Food Facts account

[teolemon]

Problem

• It's not clear what are the advantages of having an account are

Solution

• Add a message about the benefits:
  • Being a part of food transparency, and being able to contribute
  • Getting credits for your Open Food Facts contributions

Mockups

Part of

• #561

[g123k]

@teolemon Do you have a text for this?

[monsieurtanuki]

@teolemon We could add it too on the new "checkIfLoggedIn" dialog, either full or with a "more about it" option.

[prathamsoni11]

Is this screen still exists?

[M123-dev]

Yes if you are logged in and tap on your name

[prathamsoni11]

Yes if you are logged in and tap on your name

You mean this one??

[M123-dev]

Yes, the page you are on, not the one you marked in red.

Though I think it would make more sense to put a little text on the signup form, wouldn't it