I would caution against collecting usernames and passwords - even if you have no bad intentions, it makes your service an attractive target for attackers who are interested in intercepting these passwords!

I had no intention of storing it, i was thinking fully client sided.

It looks like it's not possible to call the API's directly from my JS because of XSS requests on Lemmy servers, so I'll just make it so you can choose an instance 🤷‍♂️

if anyone comes up with something else (maybe a browser extension?) can open a new issue

This might be possible with an instance custom setting to allow CORS from us.

LemmyNet/lemmy#3191

Re-opening as this may be possible as long as CORS is configured correctly (*) on the instances.

Sites would need to configure LEMMY_CORS_ORIGIN=*

This is possible and I use it for lemmy modder. I'll have to re-visit this in the new year