Ranking metrics

[sinpe13]

Hi @MaxHalford,

I have started to work on Ranking Metrics (#1419) and have a PR ready to send in for the precision@k, recall@k and f1@k metrics, however the PR screen told me if I am a new contributor, then comment here first. I want to get some feedback before moving into the other metrics in case I am off, so that I can make adjustments. I am new to the codebase and pretty new to open source in general too; so feedback would be welcome (it is all my code as my main goal is learning and contributing, only using AI to ask questions about codebase/my code etc).

Let me know how you want to proceed.
Cheers,
Peter