Add 'untagged' filter/tag

[filcuk]

Per title, to help review/organise any notes added in a hurry.
Thanks for your consideration

[ZhFahim]

At the moment, notes without titles can be found by searching for “Untitled”. Would you be looking for a more way to find untagged notes? Happy to hear your thoughts.

[filcuk]

The scenario I imagine is adding a number of notes (including titles), then going back later to review, delete and tag those notes.

What I would propose this is that there is a tag which includes any notes with zero tags, e.g.:

[ZhFahim]

Ah, that makes sense. We can add an option for filtering untagged notes to make that easier.