Switch to v2 addon

[mkszepp]

• BRAKING: move addon to v2 (embroider / ember-auto-import v2 is now required)
• BRAKING: there is necessary to add <BasicDropdownWormhole /> manually in application.hbs, because contentFor doesn't exists for an v2 addon see installation guide
• BRAKING: css import must be done manually (this is only braking for apps which are not using less/scss see installation guide
• BRAKING: For less there is necessary to add import path in ember-cli-build see installation guide
• ENHANCEMENT: Add missing properties to interface
• INTERNAL: switch from npm to pnpm