Adding documentation

[notrodes]

this is not ready for a merge, just let me know if this is a good idea!

[psvenk]

This seems like a good idea. I would put the typedefs in a separate types.ts file, specified using regular TypeScript syntax (export type TableDataObject = { ... }), and have one import block like this:

/**
 * @typedef {import("./types").TableDataObject} TableDataObject
 */

[psvenk]

TODO (when reviewing this for merge): remove merge from origin to feature branch so that history is cleaner