Remove Cadmus UI PG Library

CurrentItemBarComponent and CurrentLayerPartBarComponent were moved into @myrmidon/cadmus-item-editor from library @myrmidon/cadmus-ui-pg which had no other code and has thus been removed. This is a breaking change which avoids potential circular references and removes the need for this tiny library.

Upgrade

To upgrade your app:

1. update @myrmidon/cadmus-item-editor (16.1.3 or higher).
2. remove package @myrmidon/cadmus-ui-pg altogether (pnpm uninstall @myrmidon/cadmus-ui-pg), then change the imports in your components accordingly (just compile and wherever you get an import error replace @myrmidon/cadmus-ui-pg with @myrmidon/cadmus-item-editor).