Adds JSDoc support for EventManager

[niklaswallerstedt]

This PR enables typechecking for JS and the Event Manager class.

Since the project is mostly written in javascript, I thought it would be suitable to start to add gradual types to the codebase. I've only started with the Event Manager class for you to get a feel of what it might look like and the DX around it.

• Enables types for js, but do not enforce it
• Refactors types for simpler testing
• Updates tests and types
• Adds typechecking to Event Manager
• Updates package-lock version mismatch
• Fixes tests that broke after tsconfig change

[netlify[bot]]

✅ Deploy Preview for electrodb-dev canceled.

Name	Link
🔨 Latest commit	039e6a607f056810b52a8847613b32446a52f056
🔍 Latest deploy log	https://app.netlify.com/sites/electrodb-dev/deploys/655904dfee9fe400088b0b34

[tywalch]

This is week is crazy for me, I hope to review this over the weekend 👍