Add an automatic group for ungrouped habits

[thiswillbeyourgithub]

Hi,

I find the current way of managing activities imperfect and would like to suggest this : there needs to be a dynamic group of all the activities that have not been manually added to groups. Currently, appart from cycling through all the activities in the settings you can't be sure of you have checked all of them for the day as it gets hard to keep track of more than 10 habits.

Thanks a lot 😊