[JOSS] General explanation of reduce/preserve about scores

[tennlee]

Thanks for this feedback. Most of the current notebooks are very much 'per score' rather than 'per concept'. It will take some time, but I'll happily create a tutorial which specifically addresses the purpose and use of reduce/preserve. The MAE and RMSE tutorials do demonstrate this briefly, but I agree some more explanation would be useful for many.

[tennlee]

I would like to clarify my earlier comments. I think such a notebook could be of particular value for those outside or new to the field, which is what I meant when I said "more explanation would be useful for many". As such, down the road, I do intend to add a new tutorial specifically about these concepts. In the meantime, there are some examples in the existing tutorials.

I think the main audience for scores will already be familiar with the general concept of dimensionality reduction, and be fairly comfortable using the preserve/reduce functionality.

[tennlee]

Fixed by #589