Big Give notifier

Sends Slack updates about how the Big Give is going.

Setup

1. You’ll need to set up a Slack workflow that runs on webhook trigger, and sends a message containing the data it receives
2. You’ll need to add the trigger URL as a repo secret called SLACK_TRIGGER_URL
3. Add the Big Give campaign ID as a repo variable called BIG_GIVE_CAMPAIGN_ID
4. Uncomment the schedule stuff in the GitHub workflow

Format code

ruff check --select I . --fix
ruff format .