Prepare for Plone 6.2

[mauritsvanrees]

Plone 6.2.0a1 is available as of today. Could this be made available somewhere already? Or do we wait for the final release? I don't remember how we did this for previous minor versions.

See also #90 for Volto 19.

[davisagli]

A while back I started #91 to add demo.plone.org/next (which also happens to be a way to demonstrate the new subpath feature in volto)

It needs a few things:

• review from someone familiar with the demo Docker stack (@fredvd?)
• update to latest versions of volto and Plone 6.2