Code based on (but not identical to) https://github.com/jakelazaroff/activitypub-starter-kit
Instead of using node/express, it's using Bun/bun's inbuilt server
Right now it can follow/unfollow (be followed/unfollowed) and create notes which get sent to followers
No UI yet
Stores posts as markdown with YAML frontmatter
Stores activities for creating those posts as json
Stores following/followers in json files
