Describe why there is no create options at the content root

[nielslyngsoe]

When a user opens the create dialog on the root of the tree, but doesn't have any DocumentTypes allowed for creation in the root, the user sees the following screen:

Instead, we should allow all Document Types to be created at root, and thereby list them in the dialog. Or mention that a Document Type should be allowed.

And if there are no Document Types in the solution, we should show a screen describing that and link to the Settings Section, potential a direct link to create a new Document Type.

Something similar to this dialog, this example is taken from the create dialog on a content-node:

[kjac]

@nielslyngsoe this used to be the case. But if you have a look at #6580 you'll see why it isn't any longer 😀

Instead of listing all content types at root when none are configured, #6573 was introduced to aid newcomers in setting things up correctly.

[nielslyngsoe]

@kjac thanks for highlighting that. Well good perspectives, we just need to ensure that newcomers don't reach a dead-end.
I will be back with an updated issue! :-)

[kjac]

@nielslyngsoe turns out the changes added in #6573 to help newcomers didn't work at all 🙈

#7635 fixes it 👍

[nul800sebastiaan]

Fixed in #7635