Allow users to select the `plonetheme.barceloneta` version

[me-kell]

Why not let the user select the plonetheme.barceloneta version? Instead of hard wiring the version as dependency.

Having the version as a dependency is of course a progress compared whith the previous versions of bobtemplates.plone.

https://github.com/plone/bobtemplates.plone/blob/b79cbb13dfe5d21759c1d315e44d776be12946d7/bobtemplates/plone/theme_barceloneta/src/%2Bpackage.namespace%2B/%2Bpackage.name%2B/theme/package.json.bob#L26

But both bobtemplates.plone and plonetheme.barceloneta have their own version history (and Plone itself too).

Why not use a default but let the user select the version in a variable?