Add "Between" Target Type

[GabrielDTB]

Currently the options for target type are "at least" and "at most". "At least" works for many habits, such as exercising, where exercising more than the goal would generally be good for you but is unlikely to happen. "At most" also works against many habits, such as spending money, where you have an allowance but spending any more would be a bad thing.

Some habits don't fit either of those models, though. For example, working. You want to make progress on your work, so that would match with the "at least" target type. But, you can be super passionate about it and might end up working for a long stretch of time. Working for too long can be bad for you, so that would match up with the "at most" target type. There is a healthy balance to be had, which is why I think a "between" target type would be a good addition for habits that should be practiced in moderation.