Add get month and get week

I know this is technically already possible to do by using ```happy get after (last weeks date)```, but I think this would simplify the experience for the user and be pretty useful. I think it should be based on the last 7 or 30 days instead of the literal last week/month, but I'm not 100% sure about that and I'm curious what you think.
I'd like to work on this if possible :)