This task is for adding the functionality for creating new watchlist labels and editing the names of existing ones.
- Add a form that's accessible to logged in users at Special:WatchlistLabels/edit and Special:WatchlistLabels/edit?id=<wll_id> that allows creating and editing watchlist labels.
- Add 'New label' button on Special:WatchlistLabels.
- Add edit icon button to the end of each label's table row.