WIP: German translation

• ActivityPub.php
• AdminNavigation.php
• Admin.php
• Breadcrumb.php
• Charts.php
• Common.php
• Contributor.php
• Countries.php
• Episode.php
• Fediverse.php
• Home.php
• Install.php
• MyAccount.php
• Note.php
• Page.php
• Pager.php
• Person.php
• Platforms.php
• PodcastImport.php
• PodcastNavigation.php
• Podcast.php
• User.php
• Validation.php