Add the ability to add a description field to a scope

[ry]

On the scope page it should render the description in markdown.

It might also be nice to have it for user profiles.

[jollytoad]

Would be nice to have the option for an entire 'Overview' tab for a scope, which renders a full markdown document.
I think this would be especially useful for @std to provide some general information about the standard library.

[iuioiua]

Having a small text description field and providing a link for further information might also be fine. See #507.

[lucacasonato]

If you want to work on this, please reach out on Discord. We can help you get started.

[AugustinMauroy]

I'm on it.
First part modify models.rs using string type. after creating new form (insland) on front + modify creation of scope. then modify api(s)