JS Client for ActivityPub

[RangerMauve]

🎟️ Re-ticketed from: #
📅 Due date: N/A
🎯 Success criteria: ...

Task Summary

We need an easy way to use the social inbox from other JavaScript services / scripts. Particularly this will be useful for our github actions story and future integrations

To Do

• [ ] Fill in remainder of APIs in the client
• [ ] Write tests (simulate local server)

[RangerMauve]

Part of #130