Have a look at BetterSnapTool on the App Store:
BetterSnapTool allows you to easily manage your window positions and
sizes by either dragging them to one of the screen's corners or to the
top, left or right side of the screen. This enables you to easily
maximize your windows, position them side by side or even resize them
to quarters of the screen.
I had a client show this to me and they seemed pretty pleased with it. It also has a rating of 5 stars with 3500+ reviews. I personally don't use it (no need) but from the looks of it, it appears to be a good solution.