New Parameter for Narrow Challenges

As some of y'all may have noticed, there are a few strange challenges in the Hurlers that don't follow the rule of "60% ± 10% for every level above or below the target level" - some challenges are inverted (Play a round of Blindfold Bezique), and some increment using steps that are not 10% (5%, in the case of most Neathproofed challenges).

As a result, it was determined that we should have a new parameter for Narrow challenges. Thanks to User:mzs, we now have NarrowStep available as a parameter for {{Action}}. This parameter dictates the amount by which a challenge's success chance increases or decreases for each level above or below the NarrowDiff level.

NarrowDiff will still specify the level at which there is a 60% chance of success. NarrowStep only specifies how much each level affects the success chance.

As an example, a challenge with a 50% chance at level 6, 60% chance at level 5, and 70% chance at level 4 (etc.) would use 5 for NarrowDiff and -10 for NarrowStep.

A challenge with a 55% success chance at level 0, improved by 5% for each additional level, would have a NarrowDiff of 1 and a NarrowStep of 5.