Add support for `abbr -S/--no-space`

I recently got myself confused by the fact that abbr adds a trailing space to all expansions.

This is desirable in the majority of cases, but the specific use case where this isn't desirable for me is when I'm relying on the expansion being used as the query for searching through history.

Example:

abbr -a gci "git commit -m '"

In this specific instance, when I hit <space>, I am not using it with the intention of inserting a trailing space (as I usually do), I am actually using it as a trigger to expand the abbreviation, so I can immediately begin typing my commit description.

The issue is that the resultant expansion inserts a trailing space, which I then have to delete before hitting <up> to cycle through recent commit messages. Of course, I am only using commit messages as an example here, but this applies to a bunch of other abbreviations.

My feature request would be to add support for a new flag along the lines of -S/--no-space, which would allow me to opt-out of inserting a trailing space for specific abbreviations.