Show team-folder contents on the TeamPage

[alimmroth]

Proposal

• If possible, integrate the filemanager from files into the team-page to show and manage the contents of the team-folder. Otherwise at least some of files functionality has to be mirrored in teams.
• Breadcrumbs from @nextcloud/vuejs
• Implement the viever, so that clicking a file shows it in place, when possible

Related Tickets

• Make team-folders actually assignable to a single team #2734
• Create team-folder when creating a team #2661
• Store all team-related app-data in a team-folder #2637
• Allow admins of a team to create / attach team folders #2662