Add recall metric

[KShivendu]

We calculate precision but for higher values of K, it's more valuable to optimize for recall. Therefore, we should measure it.

[ashishu23]

hi @KShivendu , I am interested in solving this. Just wanted to confirm if the issue still persists?
If not , then can I work on this?

[LukasWestholt]

What exactly is the difference between recall and precision?

[LukasWestholt]

Ok i see here: https://en.wikipedia.org/wiki/Precision_and_recall