Feature request / UX enhancement: display proposed tag after three letters instead of automatically adding to allow for new tag creation

Wallabagger automatically tag the content with the first tag found matching a 3 letter input by the user if only one matching tag is found. It is annoying if the user want to create a new tag (See #304).

For example, to add `data-science`, when `data` already exists, the user would need to add `data` , then add `data-visualization` before removing `data`.

It would be better if Wallabagger displayed the matching tag found and added the tag on tab or enter, as it is now doing when multiple tags match. This would ease the creation of new tags, even if part of the tag match an existing tag.

Thank you for your work.