Consider sharing tensorboard demo on tensorboard.dev

[gully]

Since tensorboard is working now and is semi-interesting, consider sharing a demo of it on tensorboard.dev

[gully]

It might only support scalar data at the moment, in which case it is not very interesting... But if/when they support figures, it will be neat to visualize the raw echellogram 2D fitting process.

[gully]

Ok, we have an example tensorboard posted since 2022, here:

https://tensorboard.dev/experiment/ECm7ruEuR3uyqSLk6oSQdg/#scalars

I would say sharing tensboards is a "nice to have" but not a need to have. I'll leave the issue open as a reminder.