Describe the new feature or enhancement

At the moment, when annotating interactively on a raw.plot(), any annotation created by click and dragging disappears and is not saved on release if it is shorter than ~ 100 ms.
However, once created, annotations can be reduced to a shorter duration.

For some applications (e.g. manually marking peaks, adding events), it could be useful to be able to directly create short or single-sample annotations in one step/single-click.