Documentation for `limit`

[therji-motif]

The documentation for limit is sparse, and I for some reason thought it would enforce the heap to keep the top N values. Instead, I'm not actually quite sure what it's doing, or what some practical purposes are for it? Some clarity here would be great, as sometimes my test results with limit returned "correctly" (but it was purely by chance).

[ignlg]

Thanks for your feedback @therji-motif . I will review the implementation and update the documentation accordingly. My apologies for the inaccuracy.