feat: add ppv function and update alias docstrings

[arshiaar]

Docstrings

• [x ] Docstrings complete and follow Napoleon (google) style
• [x ] Reference to paper/webpage is in docstring. The preferred referencing style for journal articles is APA (7th edition)

Documentation

• [ x] Add the score to the API documentation
• [x ] Add the score to the included list of metrics and tools

[Steph-Chong]

@arshiaar thanks very much for this pull request. It looks great.

I have made some incredibly minor feedback (that, for the most part, doesn't even matter terribly).

Also, just a heads up, that I sometimes do my code reviews in batches. So it is possible I will come back later and do another round of review.

[arshiaar]

Implements issue #681

[Steph-Chong]

Some feedback on the updates to included.md

[Steph-Chong]

@arshiaar, you may already be across this (in which case apologies for this comment) - I believe test coverage will also need to be added. That goes beyond my skill set, so @tennlee will be best placed to provide any guidance on that.

And, if you already have a plan for this, then apologies for this comment :-).

[Steph-Chong]

@arshiaar thanks for those updates. Two more pieces of feedback (which I couldn't leave as code comments).

(1) In the "Success Ratio" section of included.md, you need to add "Positive Predictive Value" in the brackets after "Precision".

Here is how it is currently rendering:

(2) In the "Precision" section of included.md, you need to add "Positive Predictive Value" in the brackets after "Success Ratio"

Here is how it is currently rendering:

[Updated with correct screenshot]

Let either @tennlee or me know if my explanation isn't clear enough

[Steph-Chong]

These changes look good to me