Update exports in package.json to work with typescript

[KarthikRaju391]

There is a bug when using y-websocket with typescript where typescript can't find the required types of the library because it isn't exported in the package.json file of the library.

This is the error:

Could not find a declaration file for module 'y-websocket'. '<LOCAL_PROJECT_DIRECTORY>/node_modules/y-websocket/src/y-websocket.js' implicitly has an 'any' type.
There are types at '<LOCAL_PROJECT_DIRECTORY>/node_modules/y-websocket/dist/src/y-websocket.d.ts', but this result could not be resolved when respecting package.json "exports". The 'y-websocket' library may need to update its package.json or typings.ts(7016)

By making this change, I was able to fix the error.

It might also be related to the issue #72

[dmonad]

Thanks!