save voting streaks#437

this suggestion may help with the burnout concerns surrounding maintaining the voting streak.

• add a “pause/save streak” item in stars shop: it will keep the previous voting streak and not let it fall back down to 0 if the person is unable to vote again within the 24h mark
• have this item be stackable: buying 5 will keep the streak for 5 days. this will be extremely helpful for people going on vacations who may not have consistent wifi to vote

what is can look like:

• [ /stars buy: save streak ] for 2 mimu stars = keep streak for 1 day
• [ /stars buy: save streak amount: 5 ] for 10 mimu stars = keep streak for 5 days

people who have all the activity classes will have a reason to use accumulated stars indefinitely. and people who do not have all the activity classes (or have other uses for stars) will have to prioritize what to spend on. either way, this will benefit any type of mimu users.