Other fixes & improvements 🐞

• Quick add bar: click the (+) in the navbar to quickly add a new feature, artifact or user.
• Linking artifacts to features has been revamped with an inline search and is now a lot quicker than before.
• Banner notifications (or "toasts") now show up at the bottom in a dismissible widget instead of taking up space at the top.
• The toolbar on the feature, artifact and user page has been cleaned up and some functionality has been moved to the overflow ellipsis on the right.
• Creating e.g. a new feature now no longer opens a modal but a quicker inline form instead.