Add setting for monthly donation summaries

[polypixeldev]

Summary of the problem

Following #10148, all users are sent an email each month for each organization they are a member of that has received a donation, without any option to opt-out of these emails.

Describe your changes

Added a setting to the notification settings that allows users to enable or disable being sent these emails.

[sampoder]

Hmm - long term we probably want to build this into https://github.com/hackclub/hcb/issues/5367 - are people asking for this? We can merge it in short-term if people are but otherwise I'm chill with us sending it to everyone.

[polypixeldev]

Hasn't been asked for (no donation summaries have been sent out yet though), just figured it would be good to have it. Building it into #5367 would be good though

[sampoder]

We've pushed these emails out a couple of times now and people seem positive about them. I think it's alright if we don't make them configurable until the big notifications rehaul